There is any recommended patches \ security patch for redhat 5.1?
 

After I install the Red Hat Enterprise Linux Server release 5.1 (redhat-release-5Server-5.1.0.2)

there is any recommended patches AND security patches that redhat recommended to install?

Talking strictly software fixes, shouldn't reading the errata, RHSA and using up2date take care of that?

I THINK RHEL5 dropped up2date, but they do have yum update. Just contact RH, that is why you have a license.

When you registered with the RHN, you should have provided an email address that they can send security notifications to.

And, as already mentioned:
# yum check-update