The wireless N card will bring the price of the G card down.. but do note that Amazon has it listed as being "discontinued" by the manufacturer. I picked one up from Amazon for ~$53.50 shipped as I felt that paying a few bucks more for a new one would give me more piece of mind than some random used one on Craigslist.
Plus, I don't think the price drop will even be that significant once the N card comes on the market. Probably $20-$30 at the most. Think about it, if they sell the G card for $50 or so, who the hell is going to buy the N card. For most people, the G card is plenty fast anyway.
You can always wait for Gamestop to release a coupon too.. get about 30% off of $69.99.