I have the movie cars playing on my PS3 in BR.
I have a pioneer VSX90TX.

It is capable of playing the following formats:

Pro Logic IIx
PRO LOGIC
Neo:6 CINEMA
Dolby Digital EX
DTS-ES
Pro Logic IIx MOVIE+THX

As well as a bunch of modifications.

How do I determine which surround format to select on my receiver? I have a 5.1 speaker setup. Any suggestions would be helpful.

When I go to that blu-ray stats website it says this:

LPCM 5.1 24 bits 48 kHz 6912 kbps

What does that mean in context with the available sound formats?

If you want to hear the soundtrack as intended, you don't choose anything. Provided your receiver can accept multichannel PCM and you have properly set up the PS3, your PS3 should be passing unpackaged multichannel PCM to the receiver.