Well, I guess we play it a bit differently. You said that you discard a guest card at the end of each round. In our case we pick a guest card on each turn, like we usually do, even if we can't place it into our café. We can pick whichever guest we like and we have to pay for it, if it has a cost. The only difference is that we immediately discard it, but only if it can't be placed into the café. You usually discard one of the free ones, but there are some rare cases when you want to spend some money to block your opponent from grabbing a really powerful guest for him/her. But if you prefer to not mess up with your opponent, you can simply agree to always discard the rightmost guest.
Cool, we will try this too.