Actually, I know precisely how to get your Mambo site referenced in Google: switch to Wordpress! I just did exactly that for exactly that reason. After three years of 6 Google visits per month, it finally dawned on me that I had a problem. My hoster of the time couldn't help with SE-friendly URLs, so I changed hosting, stripped all the interesting content and then inserted it in a new wordpress site. Tiresome, believe me.There's a SEO tab under the Global Configuration, which allows for more SEO friendly URLs. Have you tried that?
I have, but the site in question hasn't yet been indexed by Google since I switched it to Mambo, so I can't say if it works or not