I actually have a house in a small fishing village in Mexico. Most of the people here have three, four, maybe five jobs none of which are full time. They do this to make ends meet just as many Americans work just to make ends meet. At times their lives get very hectic trying to juggle so many different jobs, but they somehow make it work. Mexican restaurant owners in this little village don't take a day off a week, and certainly not two. They sit in their restaurants most of the day looking at empty tables to be open when enough people come in for them to make a little money beyond their expenses. These people could be models for conservatism. They own their restaurant property, they own the houses they live in, they have no debt, and they simply want the government of Mexico out of their way.
What most in the US don't realize is that many of the people illegally entering our country are not these hard working, honest Mexicans, but rather we get the ones that want an easy go at life. And you're right, for many of the illegals that easy go means higher crime and a larger welfare bill in the states.
You're first hand experience is spot on. While some illegals coming here may be hard workers the vast majority are coming here simply because they can live an easy life off of welfare and illicit activities.