I want to have a cost effective wedding reception, but still include a buffet dinner and provide beer and wine. Am I being realistic to want to keep the cost to $5000 or less?

It depends on where your reception is held, how many people you are inviting, and what food you are serving, etc. Many locations will cost more than others and the more people, obviously the greater the cost. Given all that, I think you should be able to do what you want for $5,000 or less.