Yes and No.
YES as we know some students have progress really well with just Pinyin focused study, as well as students who have lived in China for a period of time or who have good exposure to Chinese language through family. Basically they learn how to speak it first, without being literate. If that’s your end goal, we encourage you to learn and get fluent.
However, NO is because learning Pinyin is just Step One of learning Chinese, there are only 409 sounds from Pinyin. Of course you can not speak the language with just these 409 sounds. You need real vocabularies, which are words made up by characters, there are so many logics in the word formation that helps you to memorize and expand your vocabulary effectively. That’s also where you will find fun and true sense of achievement when you read out a Chinese character words in the street!