yes, travellers can go only on boats you get after the traveller is waitig on the port. It's because Streetpass is an exchange and the outbox for the traveller is created when he goes to port and you can't exchange what you don't have.

(sorry for the specific vocabulary and the bad english)

I'm a little confused since I'm still exchanging exports, but I think I get the jist. Thanks

Basically, if someone dosen't have import wear or dosen't have the traveler feature on, they can't go to that island.