Hi btan219,
Most free practice Tests are administered online, but some companies do offer on-site "local" events in major cities. The link that you provided is likely for an event that you will log into online (you can choose the location (home, library, etc.) - just make sure that you have a reliable internet connection.
The description of the actual event should be provided (it might be a practice Test, free class, Q&A, etc.) - in the event that its a practice Test, it will likely be the SAME Test every time, so going to multiple events will not be much of a benefit.
While these types of free events are a great way to gain some initial exposure to the GMAT, they're often 'unrealistic' in one (or more) ways: the Test might not actually be adaptive, it might not include the Essay and IR sections and you are the one who ultimately decides on how "realistic" you make the event on your end.
Taking advantage of free resources and opportunities is a good idea, but at a certain point you have to look at this whole process as an investment in your future. Trying to save money now might end up derailing your entire 'big picture' plan.
GMAT assassins aren't born, they're made,
Rich