Yeah, I have travelled a lot with my propecia without problem. In fact, last time i was in Thailand I bought 6 boxes of propecia from the pharmacy over the counter and had no trouble leaving with it. Its probably safest to put it in your checked in luggage however.
Recently when i was flying out of Amsterdam, the security people went through my carry on luggage because I had some liquid minoxidil in my toilet bag which was in my carry on bag. The EU has restrictions about having liquids in your carry on luggage so they searched my bag. He found the liquid, but in the same bag i had 3 cut proscar 1/4's in a small plastic bag. It looked so dodgy, and i thought this is going to be interesting (not to mention embaressing) trying to talk my way out of this, but by some miracle, the guy missed them and just got the minoxidil.
Meds should go in your checked in luggage unless you need them during the flight.