SOLVED. Romance, Guy’s like 18th or 21st birthday and moves to island somewhere in the US. He ends up working at a restaurant to learn from the owner. Also fals in love with the owners daughter but eventually breaks her heart. [s]

[Mai]

Searching "novel" "Mexico city" "island" "restaurant" "daughter" this novel came up:
North of Happy by Adi Alsaid.

It sounds just like your description!