You may not have known it, but it is possible to search for friends by city on Facebook!
Steps

Step 1. Open Facebook on your web page
Type www.facebook.com in the address bar, then press Enter on your keyboard. Facebook will open on your news feed.
If you are not already logged in, enter your email address or phone number and password to log in

Step 2. Click on your first name
This is located near the button Home, at the top right of the page. This will redirect you to your profile.
You can also type your name in the search bar at the top left of your news feed

Step 3. Click on the Friends tab
It sits between the tabs In regards to and Pictures under your cover photo. The list of your friends will be displayed.

Step 4. Click the + Find Friends button
This is at the top of the box Find your friends at the top right of your friends list. This will open a list titled Do you know … and including profiles of people you might want to add to your friends list.
If you have friend requests that you haven't yet responded to, you'll see a list of those above the list mentioned in the previous paragraph

Step 5. Find the Current City section in the Find Your Friends box
This is located at the top right of your screen. You can thus search for your friends using a variety of filters such as their name, city of origin, employer or even current city.

Step 6. Select a city from Current City
Click on the box corresponding to the city you want to select. This will apply a filter to the list of people you may know, and you will only see people who live in the selected city.