How can I speed up PgAdmin III Queries?
It looks like you see a difference between the clients you use.

In my experience the different PostgreSQL clients need very different times for displaying the data they got from the server.  Far the fastest was psql and then pgAdminIII, EMS SQL Manager and phppgadmin in who-remembers-what order.  

When tried with commands which return no or few rows, the difference is usually negligible or at least very small.  Furthermore, you should see the same actual time consumed (with the usual small differences) when you issue an EXPLAIN ANALYZE ... command instead of the actual query which returns the data much slower in one client than the other.