Most of us have limited time and funds for vacations. I don't think there's anything selfish at all about wanting to spend your vacation doing something you want to do. I wouldn't let anybody put it in terms of "bike over friends."

Are these friends you see otherwise, or is this a once in a great while opportunity to get together? That might make a difference, but otherwise, I'd take the vacation I want to take.

Or come up with an alternative location where you could do a lot of biking - and help set that trip up for 2008?