Sooner Gal, you are really close to me (290 and Spring-Cypress). We just tried getting out down 529 and it was so bad we had to turn around. We are staying until mid-afternoon with the hope that traffic will have lessened with the inital crush of evacuees.
This indeed did happen last year the day before Charlie when the Tampa area was in its sights. The traffice was backed up from St. Pete through north Tampa all day and into the evening. In the middle of the night things calmed down considerably, and a guest we had from Virginia had a clear sail going home at 1:00 am.
Things in your area may be different, though, since it appears a lot more people are evacuating. Just trying to give you a word of encouragement :)