Spanish and Portuguese may have similar vocabulary, orthography, and verb tenses, but “vowel reduction,” an abundance of nasal vowels, etc. make the pronunciation mutually unintelligible. Asking us Anglophones to pick up all the details from “Listen, Record, Playback” exercises is asking too much. (Yes, I fully realize that English has its own “vowel reduction” issues.) Therefore, I suggest that the pronunciation exercises stay as is the first time and add IPA hints the second or third time around.
I suggest this staged approach because it didn’t take me all that long to master such standard word-end tricks as -o → -u, -e → -i, the nasalization of tem, etc. It wasn’t till I hit tampouco /tɐ̃(w̃).ˈpo(w).ku/ that my ears failed me. Here too “am” represents a nasal diphthong. I’m sure that there are many more such words in my future vocabulary.