Although my guide says Alstroemeria can be grown in Zone 11, I've also read that if the temperature is too high (above 22C 72F has been suggested) they may produce blind ie. flowerless stems. Comments welcome.
I am a little south of Brisbane, east coast Australia, sub-tropical (about 27.9* south of equator) at sea-level, summers are hot and humid.
I have had alstroemeria psittacina variegata growing here for many years but it does better in semi-shade for me.
Of the more fancy florist type Alstroemeria, which I started buying as plants about 1 year ago, I find that they do not mind the heat, if only they have shelter from the strong western afternoon sun and some mulch to retain moisture (as they can be a little growing near to the surface). flowering once established I did not find affected by heat otherwise.