You can be a Member of 3 Food Assemblies maximum. You can leave and join them whenever you wish.
To do so, you need to go into your Account, then click on the Assemblies tab (as shown below):
In this tab you will be able to view all the Food Assemblies you have joined. By simply clicking on "Leave this Assembly" or "Join An Assembly", you will be able to change the list of Assemblies you are assigned as a Member (see screenshot below):