I went to a dentist here in Phoenix who was going to charge me over $3,000 for some dental work. So a few months ago I went down to Algodones, MX to get that work done. On the recommendation of a family friend, I went to see this dentist:
http://www.dentistsofalgodones.com/dentistsnew/bernal.html

I knew I needed a crown and probably needed a root canal, they gave me a quote of about $650, assuming I needed everything done:
Crown = a little over $200
Root canal = a little over $200
Post/build-up = about $200
X-rays = $10 or $20

The antibiotics and anti-inflammatory drugs they'd have me buy at the local pharmacy were another $15.

The guy who did all the booking, email, and phone communication for the dentist spoke perfect English, and he gave me all the directions I needed to get their office.

When you cross the border into Algodones, everywhere you look is a doctor, dentist, plastic surgeon, prescription eyewear, pharmacies, and so on. A lot of people will talk to you, trying to get you to come into a local shop. These people are paid a 10% commission if you go to that doctor/dentist, so it's best to avoid them and negotiate your own 10% discount.

It was a two-minute walk from the border crossing to the dentist's office. My dentist's office receptionist offered to walk me from the border to their office, so I wouldn't have to deal with people trying to hassle me, but I declined that offer.

I get to the office, and it was as modern any dentist's office I've been to in Phoenix. They had complimentary bottled water, a tv on in English, and gave me their wifi password.

I ended up needing all the work done. Additionally, since they had to manufacture a crown for my tooth, an overnight stay was required (I knew this in advance and stayed in the US, less than a mile from the border). It wasn't fun, but it was what I expected. After all, dental work is never fun, whether in the US or elsewhere. Well, except for that time I was given Percocet for my wisdom teeth extraction. That was fun.

Best of luck! I hope this helps. If you have any questions, feel free to respond here or DM me in chat.

Edit: I forgot to mention that for the root canal, they sent me to a root canal specialist across the street.