Ahh yes, small bikes are the main mode of transport in Guate (pronounced of course Guat-tay). Enjoy yourself. Zona 10 (viva) can be pretty hopping at times. If you get the chance, head to the Palace in the daytime. You can also head to Antigua, which is about an hour away for a day trip, or even overnight if you have the time.
I've spent a lot of time in Guatemala City, unfortunately working in some of the roughest areas like El Mezquital. Always enjoyed heading up to Lago de Atitlan to shake it off though. Be safe and enjoy. The place gets a bad rap. It's a shame as it had a lot to offer.
Buen Vijae