I only know Pinelllas County... We have the Gulfport Yacht Club in South St. Petersburg, It's the closest to you and AFAIK it requires a membership to launch there. The Clearwater Sailing Center on Sand Key, it cost $10 to launch there if you aren't a member, memberships are just under $400 a year. And the Dunedin Causeway in Dunedin, AFIK it's free to launch there but it is the furthest away from you.

There are numerous boat ramps as well...