Bring some ideas about migrant deaths at the US-Mexico Border to put into conversation with Candido's experiences in The Tortilla Curtain. Explain the possible limitations of immigrant literature (i.e. The Tortilla Curtain) when considering the political, legal, and humanitarian crises that have marked Mexican immigration in recent decades. Does fiction make the suffering of immigrants more real? Alternatively, is fiction insufficient in representing real-life miseries of the immigrant experience?

It sounds like you're going to participate in a discussion group focusing on immigrant experience, particularly pertaining to the Mexican immigrant experience. The Tortilla Curtain was written in 1995, but many of the difficulties facing Candido and America are still applicable to those crossing the border today. These include the following:
1. Many immigrants are subject to exploitation by US citizens, who know that they live in fear of being deported. In the novel, this is a situation that forces Candido to accept $20 in hush money when he is injured in a car accident, though this means he will find it even more difficult to get work and make ends meet. A good question is as follows: "What would have happened if Candido had died—would his death have been reported?" Would it have been hushed up because he was in the country illegally?
2. There is a lack of access to healthcare. In the novel, the couple's baby dies in a tragic accident, but even if she had not, her parents did not have access to a doctor even to confirm that their baby was, as suspected, blind. Children of immigrants suffer, and die, from this to the present day. They are unregistered, without income, and unable to access vital healthcare.
3. Low-cost labor and the threat of starvation is another problem. In the novel, Candido and America are forced to work low-wage jobs just so they can bring in any income at all. At times, they have to resort to rummaging in dumpsters. This is still a situation in which many immigrants can find themselves.
4. Unsafe housing is something that can lead to the deaths of immigrants. In the novel, Candido's one stroke of luck—being given a turkey with which he hopes to feed his family—actually leads to a fire because he and his wife are living in unsafe accommodations.
Relevant recent issues you could bring to your discussion might include the detention camps at the Mexican border which have, in recent news, been called "death camps" by some. Adults and children alike have been reported as dying in the cramped and unsafe conditions. Meanwhile, parents are unable to adequately provide for their children, who have been taken from them under current US government policy.
There are, naturally, many limitations to immigrant literature, particularly where it is not actually written by an immigrant. While literature can serve to humanize immigrants in the eyes of those who have never gone through a similar experience, it can also fail to capture the reality of the situation. Sometimes, people feel that they have "contributed" something because they have read a tragic novel about immigrants, but while they feel compassion for the characters in the story, this does not translate into any kind of compassion or practical assistance for immigrants in real life.
I hope this gives you something to go on. Here are some recent articles about the immigrant experience which you could also refer to:
https://www.theguardian.com/us-news/2018/feb/06/us-mexico-border-migrant-deaths-rose-2017
https://edition.cnn.com/2018/05/15/us/us-border-crossing-deaths-invs/index.html