Via optical both TrueHD and DTS-HD MA work, though in a "stripped down" fashion. They will pass the core 5.1 signal via optical, since they are backwards compatible; this is how I have mine running right now since I don't have an HDMI receiver either. To get the full benefits of TrueHD, you do need a receiver that can handle the stream via HDMI. At this time the PS3 cannot internally decode the DTS-HD MA tracks and I have heard that it will not be able to even with an update.
*edit no sooner than I said that, I read this
article and it says DTS is working with Sony to come up with a way for the PS3 to decode DTS-HD MA.
Although the current cost of a high-end receiver capable of decoding the tracks via bitstream is likely to keep DTS-HD Master Audio out of the hands of all but the most dedicated home theater enthusiasts, word on the street is that DTS is working with Sony to add internal DTS-MA decoding to the PS3 before Christmas.