While Managua does offer city bus service, usually on old American school buses, the buses are notorious for being perpetually late and slow, and the routes are confusing, often seeming to change at the last minute.  Other problems with Managua city buses range from petty crimes, such as pick pocketing, to more serious crimes such as stabbings.  The buses are very inexpensive, but if you are traveling in Managua and trying to save money, you may be better off trimming expenses in other areas. 

Managua's taxis on the other hand are relatively safe and reliable.  They are also not very expensive (a ride across the city will cost about $5 US), but are more expensive than the buses are.  If you choose to take a taxi be sure to tell the driver where you are going before you leave and to set a price for the ride.  Keep in mind that taxis drivers in Managua expect to be bargained with and if you appear to have money they will usually try to charge you more.  Also, taxi drivers generally do not expect tips.  In almost all cases, the fare is just the fare.