That error is distinct. Check that your credentials supplied are valid (including target and port), and if so ensure that the socket is established on the MySQL server. It sounds like its up and running though, so there are several causes to that. Start by restarting the mysql service and logging in through the command line interface to see if that works.
Well to make the queries work with SQLServer, you need to return it to a non-proprietary version of the SQL code. Remove the backticks. SQLServer uses square brackets. After that's done, you need to use the SQLSRV package (not the MSSQL which isn't available on Windows 5.3+ versions of PHP), not the MySQL package. Better yet, swap it completely to PDO and use a bind, since then you don't need to concern yourself with the escaping of the strings (which you are otherwise needing to deal with).
Quick glance looks mostly alright. Move that entire first block of querying and fetching into the else clause. You can't populate the $_GET['StreetID'] from the form since you don't provide it in the querystring, but you could check for both post and get (or ugh, request) for it. Given the processing doesn't display the info, I'd say just move it. Make sure you check for the existance of the $_GET['StreetID'] before attempting to read it. Change the include to a require.