I would plant them. But that's just me. Look at it this way even if you are not there to see the bloom something will be, butterflies, bees, etc.

I agree with Glenn, I would plant them. In my garden I have geraniums planted (Nov - May) and they thrive....even made it through the freezing. They don't get the afternoon soon, just morning. They don't do very well in the summer heat for me though. As for the Alstroemeria, I've not planted those before but you have peaked my interest. It's my understanding they need full sun? I'd go ahead and throw them in the ground before you leave and see what happens....and as Glenn says, let the butterflies, bees, etc. enjoy while you are gone. ;)