the SL viewer I have wont let me change the location

[Amethyst Jetaime]

I assume you mean choose a location to log into other than home or last location. 

You can type in the name of any region or sim and you'll log in there.

I am not sure if the SL viewer has this feature, but Firestorm and probably other some third party viewers do.  You can add landmarks to your favorites folder or drag them to the top of your screen to create a Favorites Bar.  You can then show those on the login screen by going to Preferences → Privacy → General and checking Show Favorite Landmarks at Login (via 'Start At' drop-down menu).

[Amethyst Jetaime]

I assume you mean choose a location to log into other than home or last location. 

You can type in the name of any region or sim and you'll log in there.

I am not sure if the SL viewer has this feature, but Firestorm and probably other some third party viewers do.  You can add landmarks to your favorites folder or drag them to the top of your screen to create a Favorites Bar.  You can then show those on the login screen by going to Preferences → Privacy → General and checking Show Favorite Landmarks at Login (via 'Start At' drop-down menu).

[Rolig Loon]

If you are using the standard Linden Lab viewer, the option is in the pull-down menu just to the left of the LOG IN button.  Type inthe name of a region you want to log in to, like Smith or Pooley.

All viewers offer this option.

[Nalates Urriah]

There are TWO sets of login options. Grids and Favorites.

Before you login open PREFERENCES.

There is a setting you need to enable a setting: Me->Preferences->Advanced menu and enable "Show Grid Selection"

You can also press Ctrl-Shift-G at login to make it show.

There is a setting Show favorites at login. It is in PREFERENCES too, I can't find it right now and have to go...