I agree, lots of plants can sometimes cut down the frequency of water changes..
Again, I urge you to test your offices tap water. It may be different from home.
Tell us the Ph and I'll comment.
Is Money an issue? Would you me more inclined to cheaper fish, or would more rare fish be nice?
Regardless, I agree that if you have basic water, livebearers would be better... I may suggest swordtails and platies... They're the same price and a bit less 'common' than guppies...
Celestial Pearl danios would be nice in basic water as well...
For acidic water... A large school of tetras would be nice... or maybe a school of 6 cardinals, a school of 6-8 hatchetfish, and a pair of angels? Well planted with varius swords as well...
Be sure to snag an echinodorus augistifolia var. Vesuvius... Very odd-looking.