If you eat lunch early enough (11:00, say), you probably won't have much of a wait without an ADR. At noon, though, we've seen a good number of people waiting.
However, if you join the Landry's Select Club, you don't need a reservation - just walk in, show your card and go to the head of the line. The card costs $25 but you get a $25 credit on your first purchase. You can also use it at Rainforest Cafe (both of the ones at WDW) and T-Rex, not to mention any Landry's restaurants near your home. For every $250 you spend you get a $25 credit on your next bill, and you also get $25 in your birthday month.