On foot, your character can travel one mile per day. All distances are based around Delta City Square being the central point in the city. The numbers in parenthesis represent how many days it takes to explore that place from top to bottom. Also, read up on any special notes about a location. These could save your life so, don't do anything STUPID! To determine how many miles it is between locations, simply subtract the difference in miles. But, all travel will take a minimum of one day (even if the difference in miles is zero).
Seeing as how Delta City is such a massive place, it is broken up into a series of sections or "rings", and these rings are encompassed by a Military Blockade which ensures that nobody gets in or out of the city. To see what locations are avaialable within each ring, just click on the link. Again, all distances are based on distance from Delta City Square (which is located in Inner Ring). Unbrella HQ is located in Middle Ring, DCPD HQ is located in Outer Ring, and Military HQ is located in Outer Ring 2.