One more question. I generally like to give $10/night to the housekeepers and something to the bellhops as well. I know this isn't so welcome in some countries. So
1) Would it be frowned upon if i did this?
2) Would it be okay to do it with US currency?

FWIW since others have mentioned the same, I'm a globalist staying in a couple weeks and never got an offer for a cash upgrade. Interesting data point.