On foot
Walking downtown Columbus should be considered safe before mid-night, it is mostly flat, with wide well maintained sidewalks. Bus stops are at regular intervals where you may encounter some homeless in the mix, who may approach you for money or maybe smokes. Usually they present no problem and should be ignored.
By car
Downtown Columbus is intersected by High St. SR 23, running N/S and Broad St., running E/W. Broad St., can be accessed from I-71 downtown. Roads are well maintained and traffic is usually not too bad except during "rush hours" when people are going to or leaving work. Rush hour can be avoided in your tavern of choice where they offer "happy hour" as an alternative to "road rage".
By bus
The COTA bus service (http://cota.com), while not by any standard one of the greatest in the nation, can take you to most important places in the city, which should be about 5 blocks away from any conceivable location you need to go to. This service costs $2 for an express bus and $1.50 for a normal bus. Transfers are free; ask for one from the bus driver when you pay your fare.