Don't be discouraged because you didn't get a reply in a week. Magazines don't usually function with the speed of TV and radio. A 2-3 month lead time is typical.

You might not ever get any reply, depending on the magazine's volume of letters and practice for responding, but your letter could turn up in the Letters to the Ed. column nonetheless. If you get a response, it will likely be a form letter or note, and my best guess it would take a month or more. The important thing is that you expressed your thoughts.