Spanish verbs have endings. "Hablar", when conjugated, has a stem "habl-" and endings. In the present indicative the endings are: "-o, -as, -a, -amos, -ais, -an." When we hear "habla inglés", the ending tells us it´s "él, ella" , he/she speaks English. When "hablas muy bien" is heard, we know for sure it´s "tú", and it cannot be anything else.
Of course, that implies we must MEMORIZE the endings and have them down pat. This takes time and effort... but language acquisition takes time and effort.
Native speakers seldom use the personal pronouns: yo, tú, él, ella, usted, nosotros, vosotros, ellos, ustedes... Foreigners do because normally they must use them in their native tongues. "Ich spreche, Je parle" whereas a Spanish speaker will simply say: "hablo."
Pronouns are used mainly for emphasis. And it is very irritating to hear Americans say: "Yo trabajo en Nueva York" when "Trabajo en Nueva York" suffices. However, we all have the freedom to say whatever we want, at least in the west, where we can still break grammar rules without ending up in jail. Small consolation indeed.