You can get replies without return postage, but it really depends on the celeb.
I think with Jayma Mays there are usually long wait times for items to come back anyway, check out her previous feedback and that will give you an idea.
If you have any future US requests Bri0626 here on the forum sells US stamps, or you could send 2-3 $1 bills with your letter, available through a bank, post office or travel agent.

Hi

http://www.google.com/#q=Forever+Postag ... 52&bih=708

Fanmail

Hi, I'm from England and when I sent my first Jayma Mays fanmail they still did IRC stamps and I got an signed photo back from her and then I sent my second fanmail to Her but this time they don't sell the IRC stamps because they discontinued here in the UK and also in the US but I sent it anyway, and it's been nearly a year since I sent it to her (before her bday or after her bday 16th july 2012), and now I don't know if I'm gonna get it back. can anyone help me? does anyone know if I will get a reply? or if theres still a chance to get a reply? or If anyone has got a reply from a celeb without the IRC stamps? If you can help I would be so so grateful!!