Is it safe, and how can I delete mysql.sock before mysqld start?
The only way to avoid manual deletion is relocate mysql.sock
Add this to /etc/my.cnf
[mysqld]
socket=/tmp/mysql.sock

/tmp would be a good choice since /tmp gets wiped out on each server reboot
Make sure mysqld has chmod permission to write mysql.sock to /tmp
Give it a Try !!!
UPDATE 2014-03-21 11:37 EDT
If you cannot get /tmp/mysql.sock to be made, there is a hack you can try.
Run which mysqld_safe
This will tell you where the mysqld_safe is located. When I run it I get
sh-4.1# which mysqld_safe
/usr/bin/mysqld_safe

Open the file in vi, got lines 612-620. I see this
safe_mysql_unix_port=${mysql_unix_port:-${MYSQL_UNIX_PORT:-/var/lib/mysql/mysql.sock}}
# Make sure that directory for $safe_mysql_unix_port exists
mysql_unix_port_dir=`dirname $safe_mysql_unix_port`
if [ ! -d $mysql_unix_port_dir ]
then
  mkdir $mysql_unix_port_dir
  chown $user $mysql_unix_port_dir
  chmod 755 $mysql_unix_port_dir
fi

You could add this line before it
rm -f /var/lib/mysql/mysql.sock

This might do it for you
CAVEAT : Remember, this is a hack. Should mysql not be able to start for you, I will disavow any knowledge of your actions going forward.