You are in for a great time Vetter! Try this link for an overview: http://www.texaswinetrail.com/winerie....
My recommendations would be Alamosa Vineyards (some of the best quality wines, IMHO) and Fall Creek Vineyards (excellent wines in many styles and beautiful scenery at the winery and in the lake area), both NW of Austin. There are maybe about a dozen wines within 30 minutes of Fredericksberg. My favorite is Becker vineyards. Wonderful selection of many varietals. SW of Austin you can try Dry Comal Creek and Sister Creek wineries. Both do well-crafted wines in pretty locations. I think both charge a small amount for some of the better quality tastes, but it's definitely worth it.
Don't forget to allow some time to sample BBQ at places like RO's Outpost, Opie's, Cooper's and the Salt Lick, depending on which direction you're going.
Be aware that the prices the wineries charge for the bottles are often a bit more than some of the prices Austin wine stores sell them for. However, the wineries often have selections that they don't give to their distributors, especially with respect to reserve wines. Salud!