depends what doctor and hospital you go to. Some do and even if you did use that method I'm sure they'd understand (assuming they speak good enough english) I'm sure they would. I know for me (in a different hospital to what you will be in) I was given a book with translations in it (you may get something like that as well). You can just point to the translation (heavy pain, moderate pain, light pain). OR just say "pain", I know they do understand the word "pain" as it was the first thing that came out of my mouth when I woke up and they hooked me up with some sleepy time morphine asap. OR whenever I pressed the nurse button I'd just say pain and they'd check the drip to see if it was ok to administer some more, it was a pretty standard/set amount just in the drip. Maybe just determine it by how loud and how much you stress your pain level. 1 = "I haz a pain" *points* ---- 10 = "PPAAAAIIINNNNNN!!!!!!!!1". If it's a ten they may give you an injection!
xP