yeah dont use them in the city
seriously, you will face signal problems using them in a hi rise area. and you are very unlikely to get any quoted range as that range is likely to be quoted for an obstacle free path and going by the reviews that would be an expected maximum. In practice expect less and in a hi rise city area substantially less.
Thats why there are Cb radio clubs that put repeaters on high buildings etc to increase the coverage in such area. Maybe there is a club repeater that you can use. You will have to do some investigating.
Dave