showing only events that are near to the user is very difficult:
1. You need to get the location of the user (via Form or via GPS from its mobile phone)
2. You need to use the google-api to calculate the distance between the user's location and your event's location
3. You need to filter only those events that are in a specific radius, that should be configurable, around the user's location.
It's not done easy via override because you need to enhance the models of JEM etc.
1) I get user location with GPS or internet provider location
2) I use the venue location in logitude,latitude (that I insert from administration) and I show only events in 80km radius (for example) or in the same region. This can be done with a sql query if distance is in "as the crow flies"