Actually in some ways it is easier to convert from PostgreSQL to MySQL than the other way around, because it is PostgreSQL that is the "strict" one. Many values which are allowable in MySQL will not be allowed in PostgreSQL, such as dates with 0000-00-00, etc...
So, if you just dump the basic table definitions, and remove ALL constraints (including the CHECK constraints you might use in a table def) you might be fine. (Foreign key constraints can be put back into place if you are using InnoDB, but I think they will have to use the simple REFERENCES syntax, rather than the CONSTRAINT syntax that you find in a PostgreSQL dump.
Also, of course, you will not be able to use any views, rules, domains, schemas, functions, user-defined operators, INTERVAL datatypes, or any of the other extra PostgreSQL datatypes. (...have I dismayed you yet?
Oops... I just remembered; you will also have to remove all reference to PostgreSQL sequences and replace them with the auto_increment syntax in MySQL.
Basically, if your application has any complexity, DON'T convert it to MySQL. At least do yourself the favor of using SAPDB or Firebird SQL, both of which have windows versions (SAPDB actually supports almost all the same features as PostgreSQL).