In my neck of the woods (northwest Missouri), the common pronunciation of "ukulele" is "yoo-ka-lay-lee". When I started getting more and more into the ukulele, I discovered that the actual Hawaiian pronunciation is "oo-koo-lay-lay".
So...I started to try to pronounce it "correctly". To be quite honest, I felt completely ridiculous saying it the right way. On top of that, if I go to a local music store to ask for "oo-koo-lay-lay" strings, I tend to get a strange look coupled with a reply of, "Do you mean yoo-ka-lay-lee strings?". So I gave up trying the right way and just settled for the pronunciation that I've always known and heard around here.