I am a second year biotechnology student, with a minor in computer science here at CSUSM. The main campus is about 15 minutes from the closest beach (you can see the ocean from the 5th floor of the library), and about 25 minutes from downtown San Diego.
First off, I am going to be completely honest. I did not particularly fall in love with CSUSM - immediately. I did not live in the dorms, I lived in some nearby housing off campus. I found it really hard to meet people, until my second year when I started getting to know people in the biology and chemistry departments. Yes, it is no secret that the university has the reputation of being a commuter campus. Maybe it is, but I can tell you that the quality of your social life depends on how much effort you put into it. I was frustrated because I wasn't getting the "college experience", but this was not a fault of the college's, but my own. As soon as I joined a club and began to put myself out there to others in my department, it got better almost instantly. I have had an amazing time since, and it was all because I took some time to take my nose out of the textbooks. The social life here will not throw itself at you, but it is here, so you get what you put into it.
There is plenty to do in the area. There is hiking in nearby Elfin Forest, and beaches in Encinitas and Carlsbad just 15 minutes away. If you get bored there, you can take the sprinter train straight from campus to Oceanside, which features, guess what, more beaches. And if you get bored of the beach, head to downtown, where there is plenty of shopping, clubs, etc.
The campus: it is brand new, just over 20 years old. The building are very nice, and kind of have a private school feel to them in both architectural aesthetics and in quality. Not bad for $3500 a semester (if you're in state).The campus is growing very fast. They are opening up a 89,000 square foot student union in the Spring 2014 semester. They also just broke ground on two other buildings, and that doesn't include the brand new dorms that going up as well. Only about a third of the campus has been completed, so construction will be a part of the life here until it is completed.
The quality of education. I can only speak for the biology and chemistry departments here, but I have found it to be pretty amazing. The professors provide a rigorous, challenging program. You will have to sacrifice most of your social life if you wish to succeed. However, the professors are always there to help if you need it. Go to office hours! It's a great chance to get your face known, and to get a better understanding of some of the material.
They also have many research opportunities for undergrads, where you get to work in an actual lab on a project with a professor. It looks great on a resume. San Diego is a great place to be a science major because lots of job opportunities.
For incoming students, I would highly suggest living on campus for at least one year. It will allow you to meet people that you may not see otherwise. It will certainly help making friends easier. I would also suggest joining clubs. Just put yourself out there, and the rest will come.
Oh, there is one bad thing about this campus, and that is the price of parking. It is pretty outrageous: $350 a semester. Yep.