What should I do? Should I fight this or pay for it?

In general this is a cost benefit analysis that only you can make.  A stop sign violation carries with it points.  Those can affect your insurance rates and create various other issues.  While it is a minimal violation, there are violations that can be negotiated as outcomes that do not carry points.  The fines often change though.  Remember you only have 10 days from the receipt of the violation to enter your plea.  Many people take the time to talk with a local attorney who can tell you what options are available in the court that you are charged.