How do you get from San Miguel de Allende to the Gulf side

Although I've never been to Agua Dulce, I'm sure that you would be able to find a panga skipper that would take you out. However, the tarpon season is normally from April to July. This is because, like salmon, the tarpon is a migratory fish and there just isn't any out there in the other months.

Of course you can always fish for some of the non-migratory fish. Just ask the panga skippers what they are fishing for.