An adult can order a children's meal at the counter service locations. Usually, this includes an entree, one or two sides, and a small soda. I found the children's meal to be quite filling, personally.
If you're looking for a good table service location, I think your best price would be to go for a late lunch at someplace that you really want to eat. Check the menus, but lunch prices can be significantly less $$. If you'd like to eat someplace that costs $$$$, don't be afraid to ask to split an entree. Also, instead of ordering sodas, ask for water.
So, for instance, let's say you really, really want to go to Le Cellier. Well, their mushroom filet mignon would cost $34.99 at 4 p.m. (dinner), but only costs $26.99 at 3 p.m. (lunch). Two people could share a lunch of a bowl of soup, mushroom filet, and creme brulee for $40 (not including tax or tip). And certainly you could get that price down by choosing a lesser expensive entree to share or forgoing the dessert.
My point being... If you're asking for "best bang for the buck"... IMO, the best way to spend your money is to choose the place YOU want to eat and spend carefully while you're there.