Basically, yes. Small batch brewing is great for what you're talking about experimenting with different ingredients, recipes, etc.
They guys at Basic Brewing Radio do it all the time, and here's a pretty good article from BYO, but in general the proportions of the ingredients should be the same. So, if the small batch is 3 pounds 2-row, and 2 pounds wheat, the 5-gallon batch should have 66%60% 2-row and 33%40% wheat.