Weather in July in Florida.... its not bad at all!! . We are only just really at the beginning of summer in July, remember the hottest month will be August, and late August and September is when we see the majority of the thunderstorms.
You will find some Ts's in July, mainly nocturnal ones, so you will see them at sunset and early morning ( on your way back from the pub ) .
If there are Ts's during the afternoon they are isolated well separated cells, and mainly like to sit in the middle of the state over the everglade swamps, so they are avoidable, and there is wide well defined holes that you can easily slip thru to cross from coast to coast. Or you just fly a little north or south and there will be a end to the airmass causing them and you simply fly around them. The cells also come and go pretty much the way the text books say the should, 1-2 hrs and its all over.
Its also not too hot, you will find the daily temp in the low 30's, humidity around 80% , but of course you will initially feel like it 100 degrees and 100% humidity!
Airfares.... try also flights into Detroit or Chicago(
www.united.com for ORD) . Leaving from Gatwick if you are from the UK also saves money. Try
www.Delta.com or
www.Continental.com and both will get you to Fort Myers(RSW) . These three airlines will also get your to RSW with 1-2 hops in the USA.