If I'm going to be away from the MacBook Pro for a while... not too long... say, 15-30 minutes or so, or even a little longer...
... I'll just shove the cursor to the upper-right-hand corner of the display (I have the screensaver set to activate there).
The screen goes black, and I just "leave the lid open".
When I come back, I touch one of the display brightness function keys (F1 or F2), and the display "comes back alive again".
I don't even worry about it "sleeping" ... I just "let it sit there at idle".
Works for me and doesn't deplete the battery.