I have events (custom post type) at locations that I am mapping. If a location has more than one event I would like all events show up on the mashup map but only the last event at that location shows up.
I really can’t say – I don’t know how your site and data are set up. If you’d like to provide a login and a specific example I’ll be happy to take a look.
In general, it’s best to set up each location you want mapped as a separate post. In your case it sounds like you might want one post per event. You could then assign events to a location using a taxonomy, and use a mashup by category/tag to show all events or just events for a location.