Lens for Chelsea flower show (+travel)

Will be attending the 2009 Chelsea flower show and will have, by then, either the XTi or XSI with, if funds permit, the 24-105L. If funds DON'T permit I'm thinking of the Tamron 28-75.
Any other suggestions in the budget area I could look at? I hear Chelsea is very crowded so primes don't seem an option and if anyone attended and can let me know how crowded it really was I'd be appreciative. I want to travel reasonably light so whatever lens I take will have to double as a walkaround as well. It's definitely a 2 lens maximum job.

Thanks,

Hal55

Nothing wrong with either choice, both good lenses. I'd recommend at the very least to pick up the 18-55 kit lens to give you something a little wider.