I love the music and dancing ( zydeco), and the food. I also admire the attitude toward life that the Cajun people have (“laisses le bon temps roulez”).
So I think I could make a good (if converted Cajun).
On the negative side:
-I don’t live in Louisiana
-I am not fluent in the French language
So, is such a conversion out of the question?
Considering that Cajuns are an ethnic group descended from Acadian exiles, you could not become Cajun any more than you could become Eskimo, assuming you are not already.
I think a conversion is out of the question because you’re not the offspring of a Cajun. Being ethnically Cajun isn’t the sort of thing one converts to, any more than one converts to being, say, Chinese (ethnically, not citizenship-wise).
You could be (probably are, actually), a Cajun culture afficionado.
Do you like fishing?
Actually, zydeco is not Cajun music. It’s the music of the Black Creoles of Louisiana & actually did much of its evolution in Houston. Cajun music came from similar sources; BeauSoleilplays it all.
I don’t think you can* become* a Cajun but you can be a fellow traveler. Houston’s Vietnamese, for example, have perfected the art of the crawfish boil…
Knowing French is not enough - you have to know Cajun French, or one of the dialects of Cajun French, which is quite another thing.
Having lived in Lafayette for a while, here is what you’d have to do to even get close:
- become a Catholic
- change your last name to Broussard, Guidry, Landry or Thibidoux. In 1978, at least, the Lafayette telephone directory had massive clusters of a few names.
- be related to nearly everyone in town.
- be laid back. Cajuns are not normal southerners. When I moved to Lafayette I had very long hair, and no one ever hassled me about it. While there is a statue of a general in downtown Lafayette, for the most part Cajuns vanished in the swamp when they came around looking for CSA recruits.
- be ready to eat any damn thing. (T-short around the college: Cajuns are better lovers because they eat any damn thing.) Also, talk about food all the time.
That’s just a start. I just knew a few at the university, my wife worked for a Cajun company, and the ladies who worked for her were all natives.
Sneer at any dish that contains tomatoes. 
I love fishing.
I also love shrimp, crab, lobster (sorry, no crawfish up here).
But oysters…oh yeah!
I also use a lot of Tabasco sauce.
So maybe, I’m close!
As long as you like fishing, you stand a fighting chance of becoming Cajun. If not, forget it!!
I am from Louisiana and I live fairly nearby you so I could teach you some of it but I am not cajun either although it tends to spill over into other parts of Louisiana culture. My SIL is cajun however. True cajuns are fairly rare but they certainly exist into the present day. I know a few of them and know where to find a lot more if I needed them. They are a very interesting culture. Sadly, Cajun French was coming very close to extinction a couple of decades ago. It still is as a 1st language but schools have made an effort to teach it in historically cajun areas so that it survives in some form. Lots of cajun words still get mixed with English in cajun areas.
I don’t think you can be a true cajun convert. That takes a lot of history you can’t get by learning.
You may enjoy this free film on a true Cajun Mardi Gras which is very different from the New Orleans Mardis Gras (New Orleans isn’t historically cajun and never has been contrary to popular belief; New Orleans French culture comes from different sets of immigrants).
It is not just seafood. Go get yourself some boudin, preferably from a good grocery. A sign in one such said that a Cajun six course dinner was a pound of boudin and a six pack of beer.
Don’t trust “Cajun” food you see in the grocery. I lived in Lafayette before the day of Paul Prudhomme. and Cajun food has nothing to do with blackening anything or rubbing spices on stuff. Cajun food is made of things that grew in SW Louisiana - Cajuns were localvores before it became popular.