Stay at Lumbini hotel, there are some nearby attraction around the hotel apart from Maha Bodhi temple which takes 20 - 30mins on foot.
Most guide books say Rikshaws are not allowed in the city center, but there are spotted as a matter of fact.
Thus, if you want to save your travel money, just try rikshaws to go back to the Airport.
The town has little to do except two important things...visiting the bodhi tree where Buddha found enlightenment and visiting his cave 15km outside the city where Buddha meditated for six years without enlightenment.
The touts are aggressive and the taxi's to the airport a ripoff at 500 rupees...taxi drivers have a monopoly going between them and even locals can't get them lower than 500rupees. Staying in one of the local monasteries is your best bet for real enjoyment of the place.