Best Cell Phone Provider at UCR (and around Riverside, CA)

Hi!
I am going to switch to a new phone soon and just wondering what is the best cell phone provider at UCR (AT&T, Verizon, T-mobile, etc.) I currently use Virgin Mobile (which uses Sprint’s network), but it’s giving me very poor signal around campus and around the dorms. I’ve heard some good news about T-mobile. Any suggestions? Thank you very much!