Complicated. Some are happy he's in jail, in a place where it's unlikely he'll escape or get the same leniency he'd have found here, others wanted him to face trial in Mexico (though we all know how that would end ) and consider extradition to be a failure of our government.
The president complained that the sentence was inhumane and was criticised for caring more about him than his victims. Some people agree that it was too much, while others want even harsher punishments and the guarantee that he will not be able to appeal his sentence. Still for others, dude exists as some kind of folk hero, with a clothing line being released by his family and already becoming quite popular (something I personally find disgusting but to each their own I guess).
I don't know how secure the place he's been sent to is, but I would like to think it's tunnel proof and that the people working there are properly paid and/or their identities kept hidden in order to keep them safe.
The government is exploring the options they have to seize all assets though if I understand correctly the US government has dibs on all that stuff?
There's also the concern that his sentencing may worsen the current territorial wars, though security officials say that this is unlikely as the current factions have been going at it since before the official sentence was dictated and they do not think anyone else will join the fray all of a sudden or that conflict will escalate further. Some officials have actually argued that things will improve but I think it's more likely that aliens will pop up and say they visit earth to buy pizza.
Personally, while it won't change much about how things are going, I would have liked a harsher sentence (or at least, several life sentences in case they manage to appeal or something), I also disagree with anyone who thinks that he should have faced trial and prison in Mexico, there's no way that would have worked, he'd have escaped already, our system is too fucked up and useless to handle something like this.
So yeah, kinda all over the place but that's how it is over here with stuff like this.