Salty seadog
Space Cadet...(3rd Class...)
If it's a good cafe there will be other patrons there, cyclists or not, who you can ask to keep an eye on the bike while you nip inside.
We also use one of these:
View attachment 362775
I have one of those too....
That and taking an off duty Met Police officer with you.
I also sometimes have one of these with me too....
I'm covered.