macbook pro wifi won't turn on

About two weeks ago my wifi signal began to get very weak (the loading bar would show a small amount of blue, like it does when its loading a website). Its been one month since I upgraded to Lion and until recently everything was fine. I can get internet when connected to mi ethernet cord- but this *****!

I called apple support and spent over two hours fixing the problem- alas it only lasted for a short time, maybe an hour tops.

Bottom line- until this issue is figured out, and fixed by apple, can I go back to the previous mac os 10 or whatever came before Lion? I just want my wifi back- I'll give up the new features- wifi trumps all that new stuff. Help!!