Our experience was ok. We had our training session down an alleyway that smelt of strong urine, which was not pleasant. We then went out onto the main roads of south beach, which was a little unnerving. Alan, the member of staff who took us out was really good and very patient, however my partner did come off of the Segway on a main road and not only badly damaged his ankle, but nearly got run over by cars traveling at 40mph.
I would only recommend Segway riding if you stick to the boardwalks. If not make sure at you wear a helmet and pads.