If I have auditioned for and accepted a role in a local, community theater production, is it acceptable to drop the show later if something else comes along I like better?

No, even small, local theaters take role acceptance very seriously. There is no contract, so they cannot keep you from dropping out, but doing so often will burn your bridges with the producing and artist team. Choose your projects carefully, and keep the lines of communication open. If you have auditioned for more than one show, it is possible to ask to wait to accept the role until you have heard back from both opportunities. However, the offer  of a role may be rescinded if you don't accept right away. Most companies will not wait longer than a few hours/few days to hear back whether you will accept the role or not. Once accepted, dropping out of the show for any reason other than personal or family emergencies or health situations is generally frowned upon.