I think your biggest problem will be wet from below, not water sitting on the plants. It doesn't appear so, but their leaves are arranged in such a manner that water will efficiently drain from them through tiny channels. Even if some water might somehow lodge there for a while, Agave leaves have a waxy cuticle which will protect them from pooling water.
Orienting the plants to help water drain away will only work for one wet season, as they will slowly turn to face the light as they grow.
Your best bet is to select species which you've seen growing in your region. Some catalogs will address winter hardiness with respect to wet and cold. Plant Delights Nursery of Raleigh NC offers a good selection of Agave with valuable comments regarding hardiness in their climate. They say that they have trialed all of their landscape plants outdoors. The owner, Tony Avent, says that he considers every plant hardy until he had killed it at least three times, and if you read his extensive writings on the nursery site, you can tell he means business.
