Is the file-system formatted as fat32 (vfat)? If so, use the umask option in /etc/fstab to allow anyone to write to it:
/dev/sda4 /mnt/dongle vfat noauto,users,rw,exec,umask=0000 0 0
If it is fat32 though, it won't support symbolic links. You could try tar'ing them up or formatting the file-system as a native Linux file-system (ext2, etc.). It depends on how portable you need the data to be.