As a former good Cantonese speaker, now terrible, let me assure you that there is no way to ask anything nicely in Cantonese. It's a rough-and-tumble, loud, crude, obnoxious gutter language. It's awesome. So much better than Mandarin. There's a reason why Cantonese is always the go-to language for "misc bizarre foreign language spoken by asians in the background" in movies, well that and the very high number of first-rate actors available from Hong Kong's movie industry. It's my favorite language in the world.