I had luck looking for speakers by looking at guilds in other cities like Houston and reading their newsletters.
They are still building the page but Texas Association of Quilt Guilds (north Texas) has a page of teachers under resources.
http://taqg.org/teachers/
Grace Errea was a good speaker and we contacted her about 6 months out to fill a gap in our schedule.
http://www.amazingquiltsbygrace.com