No you will not need a letter for Electrolysis. I live in Florida also and I have a lot of experience with both Laser and Electrolysis. I can say that I originally had laser done at my dermatologist's office and had only positive experiences the first year. I had to switch to Electrolysis because all that was left was blond hair, the first place I went to was horrible I found another place and the experience is somewhat more tolerable.
I will second what ZoeM has said whether you go in boy mode or girl mode whether you tell them why you are having it done or not, they will know what is up. Every place I went to knew why I was there, I only presented in boy mode and never said anything, but each time they knew. I had one technician tell me not to worry about hair in certain areas (around belly button) because "a lot of women have the same problem" she would also give me skin care advice "that all women use". She was always trying to drop hints that she knew, she was very polite about it.
The horrible place I went to was not so polite about it. I went twice, on the first visit the receptionist was extremely rude and you could tell she did not want me there, the technician was also very cold and I could tell uncomfortable about it (I almost told her just so I could see her reaction). On my second visit I got the same behavior from the staff except this time while I was sitting in the waiting area several other employees came into the receptionist's office and I could see that they were looking around the corner pointing at me and whispering/giggling at me. The technician was rude again, so I never went back and found a new place with much nicer staff.
I am not a very big person (I have always been referred to as "little") so I think they found the whole experience amusing, however if I was a larger person and seemed more threatening I am sure they may have been very uncomfortable about me being there. You should keep this in mind if you live in a more rural area in south Florida or central/north Florida, this is redneck country so you will need some street smarts and thick skin!
Also FYI, Marci Bowers has a list of genital laser/electrolysis providers for her patients, there are a few in Florida and they see people like us all the time here is the link:
http://www.marcibowers.com/grs/hair_removal.htmlGood Luck
