Hi SillyMemo,
Before you spend a lot of time applying under conjugal partnership I think you should look at the guides and perhaps consider getting married. It would be terrible to lose all the money and time waiting only to be denied if there was something you could have done from the beginning to make sure you have the strongest application possible. The requirements are clear and can be found on the links I list below.
I am no expert on Conjugal Partnership but the guides say
You should not apply as a conjugal partner if:
* You could have lived together but chose not to. This shows that you did not have the level of commitment required for a conjugal relationship. (For example, one of you may not have wanted to give up a job or a course of study, or your relationship was not yet at the point where you were ready to live together.)
* You cannot provide evidence there was a reason that kept you from living together.
If your partner is Canadian then normally he would be admitted to Mexico without a problem and therefor perhaps you may not qualify for Conjugal partnership unless you can provide proof that he was denied a FM3 or FMM Mexican immigration document. (Canadians do not need a visa for stays up to 6 months, so worst case scenario he comes for 6 months on a FMM and then leaves for a while and then returns with another FMM) Has your partner been denied a FMM or FM3?
You may apply as a conjugal partner if:
you can provide evidence there was a reason you could not live together (for example, you were refused long-term stays in each other's country).
http://www.cic.gc.ca/english/immigrate/sponsor/spouse-apply-who.asp#conjugal
You can also look at the OP2 Immigration Processing Members of the Family Class Manual to better understand what you need to do to qualify and how your relationship will be assessed.
http://www.cic.gc.ca/english/resources/manuals/op/op02-eng.pdf
Section 5.25 Characteristics of conjugal relationships
Section 5.26 Assessment of conjugal relationships