Worms, as a rule, do not like bright, warm spaces. So for most worm farms, putting one on a sun porch would probably be a bad idea. A cool, dark, and damp place would be ideal. Places like a shed or especially a basement are more along the lines of what worms like.
If you place your farm outside, be sure that it is not in direct sunlight and it is in a place that always has shade. If you are in a region that has extreme temperatures - either hot or cold - it would be best to not keep it outside. A barn or shed would be a better solution in those instances.
It is easy to think of good places to put your farm. Just remember what condition your bedding needs to be in and think of a place that would help to maintain that.