I agree that ～たら is one practical tool that could express lots of meanings. but sometimes it became one problem for students of japanese.
If I say:
it's : If I go to Japan, I will visit my friend.(?)
or: When I get to Japan, I will visit my friend.(?)
it's : If I graduate (it's a possibility), I want to travel.
or: After graduating (it's certain), I'm think of traveling.
Does the meaning depend on the context? or Is there a better way to say that sentences?