i think the best solution would be to get the city to install bike parking that accomodates standard u-locks. the op's problem is that there are only trees and giant lampposts to lock to. it sucks. In nyc, there are some blocks like that, where you must go a block or so away to lock up. other times (like the subway strike) all available poles are being used. here at least, you may call 311 and go through a lengthy pain in the ass process to get the city to install a bike rack. if brighton has any similar administrative apparatus, you should get a new bike rack.

oh and seriously, every method could probably be defeated in less time than you think. i used to think the american lock & big chain combo were the most secure, but now i know those padlocks aren't that tricky to defeat. u -locks are notorious for getting pried off with a piece of scaffolding or sidewalk trash. that said, i use a mini primarily and pretty much always lock just the frame and have never been ripped off.