Jane,
Not sure about the source of your problem, bu the variable HHT is available on the PUMS files for CA. I just went into DataFerrett, created and downloaded a PUMS extract for one PUMA in CA using HHT. It worked fine, although DatFerrett acted a bit funny when I first attempted to download - I used the "batch" option to get it to work.
Tom is correct if you choose to download the PUMS files and not use DataFerrett. You can accomplish the merge that Tom is talking about using DataFerrett, but it is important to know which weight you want to use - housing (WGTP) or person weight(PWGTP). This depends on what type of table or statistic you want to ultimately build using HHT.
Doug Hillmer