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.