In a garden-level space, you'll be contending with the noise of neighbors, possibly in all directions. Passersby and neighborhood characters may also find their way into your life, in both welcome and unwelcome ways. But there's no need for strangers to remain that way, and it's in your best interest to get to know them.
Neighbors should be sources of comfort, not fear. Part of the adventure of urban living is this close proximity, and when the proper boundaries are created and enforced, it will contribute to the vitality and excitement of life in your new home.
You can ensure that this will be the case by investigating the situation before committing to an apartment. It's more important in an urban situation than in any other apartment scenario to get a sense of the surroundings and whether or not they'll be friendly. Use your wits and follow your instincts, but remember to keep an open mind.