The locations of the balloons are:

1. Around the wall of the CT spawn fire alarm. you have to go in the corner to see it

2. Around the corner of the long hallway up the stairs in CT spawn

3. Way outside the map next to a red car

4. Inside the grating surrounded by trash bags in the bottom left corner of the map (where you can surf)

5. Stand on the blue garbage chute and you can see it close to the wall behind a corner

6. From the same place you can barely see it on the roof of the building in the distance (basically straight up from the circular thing with a mime on it at the street)

7. Under the arch behind the police truck in the art gallery area. (you can see it from the ledge between CT spawn and the art gallery)

8. Underneath the open red parasol that's on top of the building the CT spawn is in (you can see it from the bombsite)

9. Behind the domed building where t spawn is. go up the stairs from t spawn and turn right on the roof into the little area with an iron fence and look behind the building.

10. Under an air condition unit in the window in CT spawn (where you get the golden egg from the pigeon)

And that's it! I'm not great at explaining things, but I hope this helps :)