Hi Kathy,
Down here in the swamp we don't finish Saltillo when it's installed outdoors. We just treat it with a penetrating sealer and leave it alone. If you don't mind doing it once a year you can use really cheap stuff like Thompson's water seal. Just roll it on and walk away. That's after you get it cleaned up and dry. Takes a couple weeks for Saltillo to dry out. Gets rained on, gonna take a couple more weeks.