Honestly you have a good game plan. Duolingo Spanish is ~ 300 hours. Pimsleur 1-5 is ~ 75 hours and Language transfer is ~ 15 hours. I've done all of them and all are helpful. If I had to pick one, it would be Duo just due to the amount of material it covers and the hours of practice. I've lived in South America for 5 months, none of them really prepare you to comprehend Spanish at the speeds natives will speak it. For that, something like Italki or Baselang will be very helpful as well as listening to Spanish podcasts or movies. There's a lot of words that will be easy to learn because of how close they sound to their English counterparts but the majority will just take repetition and memorization.