Is my sense of humor immature for my age? (20 yrs old)?

Well, yeah, humour is all a matter of opinion. I tend to not like "crude" humour (by which I mean excessive sexual jokes and toilet humour or cheap shots) much at all, but a bit of goofiness and clever innuendos can be fun at times. Absurd humour can be pretty funny as well. I can't say I'd get along with your sense of humour entirely, but since you seem to be a fairly mature, reasonable and sincere person apart from that, rather than a lot of the people who use the aformetioned crude humour, I wouldn't hold it against you. Try hanging out in a bit of a looser crowd I guess if it suits you. So long as you can be mature when necessary, I don't think it's a big deal. When you want to have fun, you should be able to follow your sense of humour that you like, just it doesn't always fit in well with a certain group.