It's been close to two years since I've driven 190 to the coast, and four years since driving to Tuxtla. There was a lot of highway widening four years ago, around La Ventosa, in some cases causing delays, and in other cases meaning that there were completed four-lane wonderful highways. But count on mainly two lanes. Of the three main highways going from Oaxaca to the coast, 190 has always been the best. Yes, there are very curvy sections, but I would not call them dangerous. They can be particularly difficult during the rainy season, with the odd washout or fallen rock, but you'll be travelling in the middle of the dry season. Close to Oaxaca there are sections of the new highway which have been opened, but I don't know if any of the sections further towards the coast can be used. Don't count on it. Regarding too curvy and dangerous, my wife and I both enjoy the drive and have done it several times .... but she takes dramamine. The hotel is what it is. I can't pass judgement because I have not stayed there, but you have two tripadvisor members who have, one of whom has provided a lot of detail.
Alvin Starkman - Casa Machaya Oaxaca Bed & Breakfast