This one comes up a lot. Met is the same the world over - I was flying in California a couple of weeks ago and there was rain and thunderstorms around....Florida is even worse with regards TS...
I did my PPL in California in 2000, now fly regularly in the USA as well as own an aeroplane in the UK. Airspace is not that different and if you did learn somewhere like LA then you will have no trouble coping with UK airspace and RT. I didn't anyway and then went on to fly from Bournemouth.
In the UK you'll experience more grass strips though, but they are no big deal, my "grass" checkout was one landing at Compton Abbas and then I was signed off. Equally somewhere like the SW USA you will experience other things, for example density altitude, mountains, and learn how to lean properly
- swings and roundaouts. I personally think that Florida is too sweaty, boring and flat.
Regarding friends - I was flying in Cali recently with a mate I met while doing our PPLs back in 2000. We still go to California a couple of times per year at a minimum for some flying (and drinking!) fun. most of us still keep in touch and meet up from time to time, and are planning a reunion next May.
The main reason to do it in the USA is that it is indeed cheaper. A DA40 (G1000) 180 lycoming can be rented for $99 per hour dry (add $32 per hour for fuel as an average). Taking all things into account, hotels, flights etc....you could reasonably expect to have a PPL in 4 weeks and save probably £3-4,000 on UK prices.
Regarding too old - I know someone who jacked his job in at 45, retrained as a pilot from scratch and now flies for Netjets.