Don't bring more than one watch. If you do you run a higher risk of being at the mercy of customs.
If you are a professional, you should know the need to declare ahead you are importing certain amount of watches with the intention of exporting them out at the end. Customs have forms for these. In years past I have read many casual collectors who did it with USA customs.
Customs are gate keepers and they will spot for anything unusual. In this society with less and less people wearing mechanical watches, if you carry a suitcase with watches, it's very difficult to explain yourself.
This has nothing to do with Baselworld but it's really a customs issue. I don't like how Baselworld is run but certain people seem to have an axe to grind with the company and took the opportunity to lump the two together. It's a personal political dick move(I am not talking about Fratello). And then you have the rest of non thinking people chiming in.
It's unfortunate that governments are tightening their grip on their customs for our little hobby. Maybe it's time we all have events in a safe and tax free haven like Hong Kong.