It's also super fun to download a 45mb menu on your cellular data plan every time you want to look at the menu.
1) All such restaurants offering free open wifi + 2) A commercialized system that hosts the menu PDFs on tiny https servers on the restaurant's wifi router and serves them locally (potentially avoiding issues with far-away outages and also saving on the internet bandwidth for the common case).
An appliance menu server would cost practically nothing if they're already offering Wi-Fi or use electronic POS/ordering systems.