My concern is that this 2nd interview is almost 2 hours long and I don't want them (or me) wasting time doing an interview without having an idea of what the salary could be.

If you feel that an addition 2 hours would be a waste without having salary information, then you should ask for it now.

Something like "Before we continue with the next step, I'd like to know the salary range for this position. I wouldn't want to waste your time or my time." should work.

Then, if the range isn't forthcoming, just decline the interview.

Be prepared if they ask you for your salary requirements.

My concern is that this 2nd interview is almost 2 hours long and I don't want them (or me) wasting time doing an interview without having an idea of what the salary could be.

If you feel that an additional 2 hours would be a waste of your time without having salary information, then you should ask for it now.

Something like "Before we continue with the next step, I'd like to know the salary range for this position. I wouldn't want to waste your time or my time." should work.

Then, if the range isn't forthcoming, just decline the interview.

Be prepared if they ask you for your salary requirements.