I'll try to answer your questions.
As for substantive work opportunities? The school has an active placement center. As I recall, there were almost always job postings for law clerk positions with local firms. So, you would probably be able to work for a few hours a week. The school does discourage too much outside work the first year, though, unless you're in the evening division. In that case, you can work all day, if that's what you want to do.
As for religion? USD is a Catholic school, but I never thought much about that while I was there. I wouldn't worry ablout that aspect of the place.
As for why I felt it was a good experience? Hmm. I went to undergrad school in the middle of NYC, so there was a little bit of culture shock at first. All in all, though, it was a nice chage of pace. I'd have to say the outdoor and recreational opportunites in San Diego are outstanding and can provide a good diversion at times. No one wants to study all the time. The school itself is fairly laid back. I'd do it all over again.