Avenal is a great place to fly with a warm atmosphere, powerful thermals and year round soaring. One of the great things about soaring is visiting other soaring sites and gaining experience in new places. Some of the sites I've personally visited and can recommend follow.
Southern California:
Northern California:
Great ground team, efficient operations and nice cool weather await at Truckee. The soaring in the summer is fantastic with flights to Oregon or Southern CA and back. It can be tough getting back into Truckee after a long flight, but rewarding to do so.
Rex runs a pretty amazing operation in Williams. Instruction, tows, rentals and repairs. Everything you could hope for in a soaring operation. They offer the best selection of aircraft for rental that you can find anywhere in the country. From an ASK-23 to the ASH-25 Open class ship and everything in between. A long tow gets you into the Mendocinos where flights to Mt. Shasta and even Oregon are possible. A great corps of experience pilots frequent Williams during the soaring season and readily share their knowledge.
Nevada
Soaring NV is the commercial glider FBO operating out of the Minden-Tahoe airport. There is a large fleet of rental aircraft and training equipment. Thermal, Wave and OLC Camps keep people coming from all over. The hospitality and fun keep them returning.
Air Sailing is a club run soaring operation, not a commercial one. Located North of Reno, it offers excellent access to the Great Basin and a great social atmosphere. It's a bit off the beaten path, but well worth the visit for their Thermal or XC Camps. Or just summertime Great Basin flying.