I would rent an Arrow.
I went to the states, and had time in a 172, but the Arrow caught my eye, and I did a quick conversion (4hrs) and went into the Arrow. I now fly one reguarly here in the UK, and it is a great aircraft - feels like a mini-airliner, and is a good step-up. I am relatively low-houred, but I prefer flying a complex aircraft (but that's just me). One thing to bear in mind is that things happen faster, since the cruise is 120kts.
You can pick up an Arrow in the states for not much more than a Warrior - plus, an Arrow will tend to have more equipment as standard.
I would recommend the advice of doing check-rides with an instructor every so often.
-- Don't forget your gear --
If your going in end of Feb/March, let me know if you are interested in sharing the costs.