Yes it is possible. Follow the steps:
1) Create a folder in ur USB thumb drive called Konami_PES and copy ur mp3 music files into that folder.
2) Plug the thumb drive into ur PS3
3) From ur PS3 menu, under the "Music" tab, scroll down to the "USB Device (Flash Drive)"
4) Press "Triangle" on ur PS3 controller to bring up the further options menu.
5) Click "Display All" and go to the folder where ur mp3 files are stored. Press "Triangle" to bring up the options and Copy the files to ur PS3
6) Back to the "Music" tab, click on "Playlist" and then click "Create New Playlist"
7) *** Name the new playlist "KONAMI_PES" ***
6) From the "Music" tab once again, on each of ur individual mp3 files, click "Triangle" on them and then click "Add to Playlist", select "KONAMI_PES"
7) Once done, Load ur PES 2011 and then go to "System Settings" in game
8) Select "Playlist Editor" and then "Add to Playlist"
9) From there, select "User Libary", u should see an option called "KONAMI_PES", select that
10) U will see all ur mp3 song files in there. Just add them using "Circle" to ur playlist and ur done. U can customize the playlist selection from there too and remove or add any tracks u want.