Yeah, when a hearing person misspells a word (like hear for here or your for you're), I just look at the context. My husband is TERRIBLE with that.
As for l337 (elite-speak), I first heard of it from my ex-boyfriend and I learned it pretty well. If I see it in a word, I can figure it out pretty good. Ofc, for me, the problem is if it's a Japanese word... in l337. I remember staring at a MegaTokyo webcomic, where a character was saying "baka" in l337. I had to IM him and ask him what it was... XD
(baka is idiot in japanese, apparently)
I know leet speak quite well but it was a pain to learn. For example 4 can either mean for or A depending on the context. I like my letters to be regular. I rarely ever use it though I did use it once to parody some gamers who think they're 133t cuz they have madz pvp (player vs player) skillz. I think they're kewl d00dz. :P I had thought elite was pronounced e-light. Nope. it's e-leet. Hence the spelling of Elite as 133t