Hi smazzoni,
I can help out with your question. There is no default way to set a default location.
I did do a search by a city and that creates a url I can copy and link to with a defauly location.
For mine I searched Arlington, VA and below is the url that I then used to open in a new browser with Arlington, VA as the default location.
http://yoururl.com/events/?action=tribe_list&tribe_paged=1&tribe-bar-geoloc-lat=38.8799697&tribe-bar-geoloc-lng=-77.1067698&tribe-bar-geoloc=Arlington%2C+VA
You maybe able to reproduce that with a Los Angles Search.
Let me know if that works for you.