They have released the new service pack 3 for 2013.  It would appear that it is very difficult to install if you purchased through the app store.  I haven't installed it yet as I am reading about all the troubles with it. As far as i can tell here is what you need to do if it is from the app store.

Install 2013 on Mac with Mavericks

Upgrade to Yosimite, do not open ACAD it may get "broken"

Download and install service pack 3 per instructions

( http://knowledge.autodesk.com/support/autocad-lt-for-mac/downloads/caas/downloads/content/autocad-lt... )

You should be good to go

Supposedly, Auto Desk will provide an install file that will have all 3 SPs included.  I however, doubt that they will if you got it from the app store. 

Here is a more complicated, method I won't be trying:

http://forums.autodesk.com/t5/autocad-for-mac-general/autocad-lt-2013-yosemite-trouble-re-install/td...

I am going to wait for a success story to be posted along with a method for upgrading.