I'm at 13%. Contribute what you can afford and what you're comfortable living with. If you can tighten your belt a little bit without sacrificing TOO much, give it a try.

edit: as far as taking it with you when you leave, 401ks are eligible to be rolled over into an IRA account. Your 401k plan should have more details but I'm pretty sure they're legally required to allow you to roll it over.