"When is lychee season?"

Almost summer, which is tropical fruit season! I'd like to ask a fruit vendor something like one of the following:

"When do lychees come into season?"
"When can we expect to see some lychees?"
"What's the peak season for lychees?"

Also, asking where the fruit was grown: "Where were these lychees grown?" or simply "Where do they come from?"
And, perhaps, "Where do the best lychees come from?"

Thanks :)