Well...
You'll find that a lot of serious shoppers sign up with over 150 (some 200+) MSC's - and are STILL signing up with companies when they find new ones.
There's no way you can ever sign up for too many. Heck, I signed up with some companies that are only in Asia - but, maybe someday they'll have a job here and I'm in the database.
Like MrC said - the only way for you to find jobs in your area is to settle in and have a go at signing up for the companies!
As far as keeping track of jobs, there are several discussions on these topics.
Hopefully you are using a spreadsheet, keeping track of log in information, URL's, PW's, UN's, pay periods, etc. If not, make sure you search "spreadsheet" - that will give you an idea.
Also - here's one topic on how some people keep track of searching for jobs:
[
www.mysteryshopforum.com]
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Proud To Be A Soldier's Mom