The two takeaways here are: learn pronunciation first, and learn the script of the new language immediately (or you'll just mentally transcribe the sounds using your first language)
Correct, and correct. All native speakers of any language are habituated to produce the sounds and perceive the phonemes of their own language, and NOT to produce the sounds or perceive the phonemes of any other language. Acquiring an understandable accent generally takes good training at the beginning.
How about starting with a CD and book of nursery rhymes and then listening whilst following the text.
Then eventually ditching the CD and reading/singing the rhymes from the book out loud.
Then (having read the translations) doing the same whilst visualising the content.
For an adult learner, CONSCIOUS awareness of the different phoneme system of the target language is almost surely necessary. For some language combinations, dictionaries with International Phonetic Alphabet pronunciation keys can help a good deal. Better quality language textbooks have a beginning section detailing differences in the sound system from the learner's native language to the target language.
What does "script" mean in this context? What is the "script" of a language?
I picked up enough Portuguese to fumble along in Brazil by taking 40 hours of lessons from Berlitz, 2 hours per day twice a week, just me and the teacher. That was kind of the minimum to make continuous progress. Group classes are way less effective, and courses at the local JC are totally worthless. The only thing that counts is how much time you actually spend speaking.
It's expensive as hell, but I strongly recommend 100 hours of individual instruction before going off on your own in learning. It gives you a good feel for the pronunciation of the language. If you learn by reading but with the wrong pronunciation, it may take a long time to recover. The proof to me was when I was in rural northeastern Brazil. The person that I was haltingly talking to said that he could tell that I was from Rio by my accent. I wasnt, but my teacher was.