i went to last years 'mango mania' in pine island, if you are referring to the cape coral / fort myers area festival. I thought it was pretty tame. I did go toward the end of the day, but it seemed like 50% of the real-estate was for selling home made crap like hot sauce and beeswax that had nothing to do with mango and the plant sales focused on plumeria with mango on the side... again this was at the end of the day on the 2nd day of the festival, it may be better on the first day and early.
Based on last years experience, i do not plan to attend this years festival. This should all be mitigated somewhat by the fact that when you live in cape coral / fort myers area you can just drive to pine island and have unlimited access to hundreds of varieties of fruit, mango or otherwise.