We usually go from around May 24 - June 6. For the past several years we've gotten $59/ow on SWA for those dates on the standard internet specials, but I'm not sure that prices will hold this year, due to fuel prices.
I think sale fares will be more likely to be in the $70-80 range, unless gas prices miraculously take a major fall.
Normally we buy our late-May tickets about 6-8 weeks out.