I had the same problem : no stored procedure methods in StoredProcedures.cs . It was empty except for the "using.." statements. I was also in MYSQL too.
After a bit digging I found the problem in the source code. Dataservice.cs has the following line :
sp.SchemaName = rdr["SPSchema"].ToString();
It's at line number 412 (ish) in GetSPSchemaCollection
This line causes an error and stops generation of the methods in StoredProcedures.cs . Simply remove the line, as SPSschema is not even in the data reader rdr, and rebuild the solution. Then the methods will appear.
A similar problem was found with the Oracle provider, it has been logged at http://www.codeplex.com/subsonic/WorkItem/View.aspx?WorkItemId=17986 and it's been fixed too.