For the VPN you must have a fixed IP address, otherwise how do you know what to connect to ? If they don’t give you a fixed IP address, change the service provider to another one who will do this.
To check the speed of response through the VPN, you could set up a webserver and run the Speedtest Mini application on there. This gives a measure of the upload and download speeds. You can get more information, and the application at http://www.speedtest.net/mini.php
Then give all the users access to the server where this runs, and they can check the speed whenever they like.
Hope this helps.