Oh gosh, I've seen two of the three - The Proposal and the Ugly Truth. I also want to see the Time Traveler's Wife, though. Decisions, decisions.
Honestly, I thought they were both fantastic and I can't wait to see the third. If you're looking for a comedy, I'd suggest either the Proposal or the Ugly Truth. If you're looking for a full blown chick flick, go with the Time Traveler's Wife.
From the two that I saw, I would recommend either because I thought they were both amazing. You'll enjoy either of the three [: