Just keep on doing the same route and you'll see progress very fast.

Also this will soon not be true:
> It's not so fun on the way back though

Some tips to make it:

- make sure that the tyres are inflated correctly
- make sure your drivetrain runs smooth and the chain is lubed
- make sure your seat height is correct (ask your LBS if unsure)
- conserve energy while climbing and use a small gear
- do not do this every day. keep it 3 days per week as you said, and don't do much physical activity (especially leg related) in the days between