Hi Andy,
Read your post and felt compelled to respond. I will not be attending the Florida Jam. Wish I could. However, as an American (though living in the UK), I can speak from personal experience to the issues you raise.
First, no need to be nervous. If you have flown at all, then flying to the States is no different. It just takes longer to get there. You say you may be flying to LA. I was born and raised there and have flown in and out of Los Angeles International (LAX) many times. You will find strict controls and very serious officials when going through Immigration and Customs in the U.S. That is the reality post-9/11. Take no notice of it all. Just ensure you have all the required documentation (passport etc.) and follow the instructions you are given and be patient.
I am sure the hosts in Florida will have the KN7000 and other instruments available for you to play. They have said so in earlier posts.
You will be approximately 2,500 miles from Florida while in LA. Is it easy to get there? Absolutely. But it is another long flight. You could fly direct from LA to Orlando I'm sure, then fly from Orlando back to London.
My advice is to go if you can afford it and have the time. You will enjoy the experience and would have a great time with our fellow forum members in Florida.
If you have any questions you would like to ask, send me an e-mail and I'll be happy to oblige.
Best Wishes,
Chuck