When you get there. Just ask a few locals where the local shops are and the better places to rent equipment. If it is your first time snowboarding, then switching boards will do absolutely NOTHING for you.
I would be extremely surprised if you were linking turns by the end of the day, much less being able to determine the strengths and weaknesses of the board you are riding.
Relax. There will be plenty of shops renting boards. It would make more sense to rent a board close to where you are staying, so that it is less of a logistic hassle to pick it up and return it.