I am actually very interested in a dual-fuel setup as well. These are being widely used in South America, as is LPG in Europe. Kits from South America are not that expensive. It's the regulation here in the US that is the problem. As you can see from the map of my area below, there are plenty of places to fill up. And many of them are almost half of what petroleum is.
Jay Leno's garage has some videos on Phil, and the Honda Civic.
http://www.jaylenosgarage.com/video/video_player.shtml?vid=193319
Hope this helps! Perhaps someone here will try it and report back. Or if there's someone in South America who can give us some better info.
Forgot to mention: Look up Galileo, they are a large company in South America, and you might even find some of their kits on ebay.
Below is what I recently posted on another forum:
According to my research, the high cost here in the US is due to Federal regulations. There are conversions available for much less than $14k, however each kit has to pass a certification by the EPA for every model and even variant it will be used in. Therefore a kit manufacture would have to pony up for each type of car they want it to be "certified" for. It costs $50,000 a piece. Our taxes are spent out the nose to subsidize corn for ethanol, and yet they won't lower the price of the "certification" for a much better alternative. The waste management vehicles in my city run on CNG. What's good for the goose is apparantly not good for the rest of us. It is reportedly safer than gasoline, and if they wanted to research it, they would. Some states have moved ahead with friendly environments, but our central government has not.
Also from my research, there are many countries in Europe and South America which use LPG or CNG with great success. The Galileo kit works on a variety of vehicles, including Toyota, and is reported to work well. CNG Outfitters in Utah does conversions and has a video or two. I am not associated in any way, but was considering making a trip up there to get mine done. Time and money will tell.
At this point the only converted engines allowed are from GM and Ford. There is a heavy penalty for being caught with an "uncertified" kit, even if it passes emmission tests, so be aware!
Here is a google map of CNG stations:
http://www.cngprices.com/index.php?location=92649&lat=33.721051&lng=-118.047883
This is an email response I recieved a few days ago from BAF, a company that does fleet conversions here in the US:
Thanks for contacting BAF. Unfortunately I do not know of any company who might convert your vehicle. BAF is the only converter in the US who has obtained multiple CARB and EPA certifications on multiple vehicles/engine families for dedicated CNG use. Today, we currently sell to fleet managers and through a few select Ford dealers who can sell individual units (and who may be able to drop-ship to you).
These are the vehicles we are certified to convert at this time (current model year, new vehicles only):
Ford F-150/250/350
Ford E-350
Ford E-450
Ford Crown Victoria/Mercury Marquis/Lincoln Town Car
GM C4500/5500 8.1L
Select Dealers:
California:
Wondries - Ford, Chevrolet - Clarke Cooper, Fleet Division
Hansel Ford - Darron Kendall
S&C Ford Lincoln Mercury - John Janes
Texas:
Westway Ford - Bruce Elliott
Please let me know if we can help you further.
Sincerely,
BAF