Lychee can easily handle zone 9b, its favored climate range is somewhere in between tropical and subtropical.
If you're not sure, 'Emperor' and 'Hak Ip', being mountain-type lychees, may be a bit cold-hardier than other varieties. 'Mauritius' is also a mountain-type but I think it may not be as cold hardy as the first two (I could be wrong). Brewster is a bit cold-hardier than other lychee varieties, it is believed. It happens to be a water-type lychee, which also is definitely obvious from the smooth exterior skin of the fruit, and the tall heights the tree can achieve.
I don't think any lychee varieties will have too much difficulty where you're at. There may be the occasional cold year but the proximity to the water should help mitigate that.