First time homeowner and needs help!

I just recently purchased a home with a large backyard. I have three huge oak trees, four orange trees and one grapfruit. There are also several plants and bushed that I am unfamilar with. I live in FLorida so the orange and grapefruit trees are already filled with fruit. The issue is that the fruit is extremely bitter and it seems the yard has been severely neglected. I have also noticed a type of black bug on the trunks of the trees that seem to be an infestation.I am very uneducated about how to care or even save these trees. I would deeply appreciate any advice that might help me!

Well, there are a couple of things that can be done to get more information.
1) Post pictures of the bugs in the forum here devoted to plant diseases (I have not looked at that forum yet, this morning. Maybe you have done this).
2) Take samples of the bugs to local experts. USDA offices, university extension offices, other.

Take some pictures of the plants you want to have us ID. Get an overall picture of the shrub or tree, and some close ups including a twig or branch with several leaves, and anything in the way of flowers or fruit. Post these pictures in the Plant ID forum. Best start a new thread with each plant. In the close up pictures include something so we can see what size the leaves, flowers and fruit are. A ruler is great.

Get a soil test. You can buy a kit and do it yourself, or send out samples. I would start with the home version. The simplest test kit includes nitrogen, phosphorus and potassium and pH.
If that shows certain nutrient deficiencies then use an organic fertilizer to correct those deficiencies.

Around here, adding organic matter to the soil, mulching the surface, and rototilling in finer material is very beneficial. Among other things it improves the movement of moisture and air through the soil and encourages soil microorganisms, and makes the pH of the soil more acceptable to many of these organisms and makes fertilizers more available. So, if this was my garden I would get as much mulch as I could and dress the areas under the citrus. Mulch will also discourage a lot of weeds. Cut down existing weeds and cover the area with mulch.
Mulch in this case is any sort of organic matter, usually fairly coarse (1" to 3" pieces are good). Spread it out so you cannot see through it to the soil. Do not pile it up against the trunks of the trees or shrubs, but get it fairly close. I get chips from companies that prune and remove trees. Around here it is free. If you like the look of it, go for it. After a couple of years it decomposes and can be tilled into the soil.
If your oak trees drop a lot of leaves, use these.

Here is a simple, 2 part DIY soil test. This will tell you if you need to add organic matter, and how much sand, silt and clay there is in the soil. Sand, silt and clay are soil particle sizes and will help determine how you water and fertilize the soil.
Part 1)
Get a small handful of soil, and get it damp.
Feel the soil between your fingers. If it feels gritty there is a high % of sand. If it feels slick there is clay in it.
Try to roll out the soil like you are making a worm.
Soils high in sand will not cling together well enough to make any sort of worm at all.
Soils with less sand, more silt and clay sized particles will be able to make a reasonable sort of worm. Higher clay soils will make a really long worm.

Part 2)
Get a straight sided jar with a good lid. A pint or quart canning jar is good.
Put some tape on the side from top to bottom so you can mark on it.
Put some soil in the jar. 1/2 to 2/3 full. If the soil is lumpy break up the clods before you put it in the jar. Remove obvious stuff like leaves and roots. Tamp it down a bit. Mark how high the soil is.
Add water. Fill the jar. Add a drop or two of dish washer detergent. Not the stuff you use to wash by hand, the machine stuff. You want low or no suds. This is optional.

Shake, shake, shake..... the jar.

Get ready with a watch or clock with a second hand and set the jar down.
Mark on the tape the level of soil in the jar.
30 seconds
2 minutes
1 hour
2 hours
Also note if there is a lot of stuff floating.
Convert these numbers to % compared to the original soil level.
Leave the jar to sit overnight.

Here is how to interpret the results:
Floating stuff is organic matter.
Sand falls out of the water in the first 30 seconds.
Silt falls out of the water in the first couple of minutes.
Coarser clay falls out in an hour or so, finer clay in a couple of hours.
Look at the water color. If it is murky there is still a lot of clay in suspension. Look at this again the next day.
The next day, the water might be clear or almost clear. This means none of the finest clay particles.
The water might be clear but tinted any shade from yellow through the oranges and reds to brown. This means enough organic matter to add tannic acid and other organic acids to the soil. This is good.
If the water is still murky then there is enough very fine clay, so fine that Brownian motion keeps it in suspension.

What to do with the results.
up to about 50% sand is pretty good.
20-50% silt is pretty good.
Over 10% clay is not so good.
Organic matter between 25-50% is pretty good.
1) If your soil has lots of organic matter you might be dealing with a special kind of soil which is called (around here, anyway) peat soils. This is usually reclaimed soils from an under water location, perhaps a swamp. You will probably also find this under the oak trees where the leaf litter has been accumulating for many years.
2) If your soil is mostly sand it will have a hard time holding water or nutrients, but water will soak in quickly. You will have to water often. Adding mulch will help keep the soil cooler and moist. Adding soil conditioner when you plant will help the soil hold moisture and nutrients.
3) If your soil has a high clay content then it will hold water and nutrients better, but you may have to apply water slowly for a longer time to allow it time to soak in. Organic matter like compost or soil amendment will help to open the soil and allow water to soak in faster, and help with air and water exchange.

You can begin cleaning up the neglected parts by cutting off dead limbs of trees and shrubs that you can reach and have the tools to handle. If there are high branches, or you need climbing gear you might want to call in professionals.

A few overall pictures might give us a better idea of what you are dealing with.

Thank you! I will take pictures tommorrow morning and post them then, (I work overnights so I will be responding and posting in the middle of the night most likely) I would say the oaks that I have (there are four) are about 100 ft tall, so I think they are consider Grand Oaks in my county and are very protected. The issue is that because the yard was so neglected and I know so little about what to do to fix anything that I am feeling very overwhelmed. Again thanks and I will post those pics very shortly.

Well, lets take things one at a time and see how it goes. I am often posting in the wee hours of the morning, too.

Here is a really quick way to assess the soil in your garden:
Are the weeds thriving? Pretty good soil.