So, first I will say to never set your heart on an Ivy or other ultra prestigious school. I was in the position where if I applied (RD, not ED) to maybe ten prestigious (defined as Ivy, Stanford, MIT, Caltech, UChicago) schools I was almost guaranteed to get into at least one. I got into two on that list as well as another ultra-prestigious school. For me, given that I didn't want to go to my state school, all of other schools were within $10 000 a year of each other (all $45 000 - $55 000) including scholarships. My safety schools (mostly U of Michigan), which I liked, offered me dreadful scholarships, so I had no motivation to choose them. This was, mind, when the recession was more of a worry. As a result, I didn't see any reason not to choose the prestigious school.
Now, I will emphasize what Ygolo said: you might be close to the bottom of your class. I had already known that I might not be near the top of my class in college, but I didn't realize that when everyone is a genius, suddenly you're taking home shitty grades. Fortunately, I want to go into industry (I'm in CS), so I just need to get out of here with a degree, and my GPA is irrelevant as long as I can graduate. (For the record, I went to an excellent, very competitive high school. I was in the top 10% of a class that contained Intel and Seimens semi-finalists, and where all of the top went to an Ivy, Caltech, MIT, UChicago, or else went to a state school that offered enough money that they ignored their acceptances to the previously mentioned schools. I thought that after surviving that sort of high school I'd be okay. Oops. I miscalculated). On the other hand, socially, I adore college. I don't have to deemphasize my intellect to avoid intimidating people (quite frankly, I'm nothing special here). If you are worried about a state school being subpar socially, just make sure to go to a large enough one. It'll have a group of Ivy level students.
As for the effect of going to an Ivy on your future, it depends on your path. If you want to go into medicine, go to the college that'll give you the highest GPA. If you want to go into CS, prestige is good, but the prestigious places are Caltech, MIT, Carnegie Mellon and some of the Ivies (Princeton for theoretical). Prestige is still non-essential though. Humanities, figure out what sort of job you'd like. Be aware that debt isn't worth it if you have a low expectation of 6 figures fairly soon after graduating (this is what makes debt acceptable for CS and Chemical Engineering, and the like). Debt isn't always worth it then, but at least it's rarely crippling given the salary. I'm unclear on the effect of prestige for business, but I suspect that if you network well, anything from a good state school and up would work.
I don't know what your financial situation is like, nor your academic prowess, but that will impact your scholarship situation. If you are in a really bad place financially, many Ivies will let you attend for almost nothing (particularly HYP), while a state school cannot offer as much. On the other hand, it's cheaper to begin with. If you are really middle class but truly incredible academically, the Ivies will offer you little money but the schools in the tier right below will be all over you offering money. If you are really middle class but less incredible academically, your state school will be the cheapest option.
Early decision is binding except that if you cannot afford the school, you turn them down. This is not recommended, but it is an option.
Edited to add:
The UCs are generally prohibitively expensive out of state. They offer bad aid, and for an out of stater, are really just not a good deal. I have a good friend who dreamed of going to UCBerkeley. She got in, and somewhat later found out that paying for it would have been prohibitive. She ended up at Harvard, which offered pretty good aid. If you cannot afford full tuition, the UCs are pretty much the worst schools to look at.