New Post: Does AutoSPInstaller install the CU's after the PU in SP2013?

Yes and No. Let us distinguish between native slipstreaming and the one AutoSPinstaller can additionally perform.

Natively, you cannot slipstream both March PU and April/June 2013 CU.

That is why on May 10th, Brian added another "updates" folder.

So now there are 2 updates folders. One is at 201x/sharePoint/updates and the other is at 201x/updates

So what you need to do is:
1) Extract the files within March PU and copy them to 2013/SharePoint/updates
2) Unzip the CU and place the exe file in 2013/updates

Hope this helps.