I had a similar question before I registered on line. When you do the free trial, you don't have the option of choosing preferences, but once you register, you can tell them to eliminate pork from your suggested recipes. There is also an option to eliminate shellfish, and two vegeterian options as well.
I have food allergies and cannot have any dairy and sometimes I just don't like what's in the recipe. What I have been doing (oh yeah, like doing this for two days makes me an expert!) is printing out the suggested menu, then going to the food nutrition log and putting in my ingredients separately. For example, I did a pasta premaveria without cheese and substituted soy milk for regular milk. I also define new foods by putting in the nutritional information from the brands I use.
I'll admit this is rather time consuming, but I'm looking at it as establishing a data base. Eventually, I hope, it will be easier. If someone has a better way, I'd be grateful if you'd share it!
LAM
SD 7/3/08 SW 202 CW 176 HT 5'3" GW 150