subordinate clauses after conjunctions

[whatever_love_means]

Must I always enclose it in commas? Is it okay to omit the comma after the conjunction? Here's an example:

"The best way to see a country is to travel on foot, but, if you are pressed for time, you can just..."
OR
"The best way to see a country is to travel on foot, but if you are pressed for time, you can just..."

I've posted this before, but I might have provided a bad example, so I'm posting another one now. Please help me...

[Tdol]

I would say that that is an optional usage, and that the comma slightly changes the emphasis, by making 'if you are pessed for time' an aside.

[whatever_love_means]

Ah, emphasis, I see. Thank you very much again.