The advantage of Duolingo is the ‘gamefication’ of language learning can be really helpful for people whose motivation declines when they find out that learning another language is challenging. In my experience, Spanish is not as complicated in terms of grammar and pronunciation as other languages such as Russian or German - in those languages, the repetition with ‘instant’ correction is really useful to reinforce concepts of gender of nouns, declension of nouns, conjugation of verbs, and choice of case.
Duolingo is not particularly good at correcting pronunciation - in Spanish, you can be pretty fucking sloppy and still have your answer count as ‘correct’. Here, there is nothing like working with a native speaker.
Duolingo does not really offer you any useful skills for conversation, or for writing on your own. It’s simply beyond what their ai and laid off course creators are capable of.
The only difference between the free version and the first level paid subscription is the ads. I doubt the ads make Duolingo Inc. much money in and of themselves - they’re just there to annoy you into paying so you don’t have to deal with them. I haven’t used Duolingo Max because of my strong feelings about ai.
The following is my personal opinion based on having worked seriously on French, German, Italian, Russian, and Spanish (as well as having dabbled in Greek, Hebrew, Gaelic, and Japanese). Your success will depend heavily on your motivation - when I first took French in junior high school, I’m sorry to say that I didn’t care about it at all, and my marks reflected that attitude. Taking German in university, I was more motivated, but I lacked discipline - if you don’t memorize the gender of each new word you encounter, you will have a real struggle when you go to use pronouns. By the time I took Italian and later Russian, I had both the motivation and the discipline, and did quite well. I’ve since gone back in French and German and applied myself accordingly.
With Spanish, it has been mostly Duolingo - I found a conversation class at the New York Public Library, but the level is pretty elementary. I’ve now caught up with a couple of other conversation classes, and I have a weekly Zoom call with a tutor for conversation. I have a score of 71 on Duolingo, but I find that plus $5.00 might get you a pupusa - I certainly cannot converse as easily with the people in my neighbourhood as I can with native French, German, or Italian speakers.
So what I’d recommend - for your short term goal, you might be better off to pick up a Spanish-English phrase book and augment your Duolingo studies with that. Showing the willingness and the interest to learn someone else’s language is at least as important as your ability at a beginner’s level. You may find people on your Mexican trip who are willing to help you advance your language skills.
Longer term, I have found a university course/extension course is the most effective way to get you started in a language - a combination of grammar, practice, conversation, and writing. You can always augment that with podcasts, YouTube videos, reading, songs, and with some Duolingo work. The downside is that it’s more expensive. The upside, for me, at least, is that I have found I progressed much further in studying with fellow human beings.
All of which is just my humble opinion, of course!
And above all, buena suerte en español!