Is it possible to get mailing addresses of all the Centers on the east coast of the United States?

You can get those from the Home Page of the SDB. -- Click the link (close to the bottom, left) called Center Table.

You can use the "Filter your selection" to choose just US centers and groups by using the "select country" menu to select the US and clicking the search button.  To get the East Coast of the States, you could just click the ones you want -- You select specific centers/groups by clicking the check box on the far right of their listing.

Once you've selected the centers/groups that you want, scroll to the bottom and click "Download to excel"

This will give you an excel spreadsheet with the centers and groups that you selected.

Important note:  the first set of addresses is the location/street address and the second set (called postal) is the mailing addresses -- sometimes a repetition of the street addresses and other times a po box or home address.