Walking on a college team is really tough unless you are playing pretty good. I would have to agree with all of the other comments saying that if you are a 20 handicap, there is probably no chance of walking on to the team, especially D1. As some of the other folks had mentioned, there are more recreational club teams at colleges these days.
Being a varsity player for 2 years of school and not playing on the varsity for 2 year, I can say college is a lot more fun if you are not playing a collegiate sport. The time and effort of a varsity team is huge. Stick to the club team and get out there to play more and have more fun.