If you are in between tall buildings on a narrow road, it can be very difficult to get a GPS fix because your GPS might only receive signals from straight up or along the axis of the road you are on, but not from the sides. In downtown Chicago while sitting under a elevated train when I was stopped at a stoplight, my GPS lost all signals. And the only way I could get a new location fix on my GPS was to pull into a parking lot where signals from more satellites could be received. I had similar problems in downtown Pittsburgh leaving from the Amtrak station, between tall buildings at a stop light, my GPS lost location and had trouble getting a new location until I traveled several blocks to get away from the taller buildings. I got lost in the old town of Prague Czech Republic while walking on very narrow streets between buildings when my GPS gave up even trying to figure out where I was. In cases like this, the best option is a GPS that has a better antennae. My older Etrex series Garmin GPS units are pretty bad at this, but my Garmin 62S has an outstanding antennae.

If your problem is the complexity of calculating a new route, if you shorten the distance of your route by just trying to get to the edge of the city at a point where you would travel past anyway, instead of entering your final destination, enter that location at the edge of town. Once there, enter your final destination.