I don't know how to read Sanskrit. Is it important to read Bhagavad Gita shlokas?

In India there are many Sanskrit scholars, but practically none of them are devotees of Krishna. Srila Prabhupada, before he went to the west, founded a League of Devotees, but the interest from Indians was very limited. And least of all, so-called scholars of Sanskrit showed no interest in Bhagavd Gita and Krishna’s message.

Then Srila Prabhupada went to the west and taught Bhagavad Gita to mlecchas and yavanas, and first then did the Bhakti movement take off. The Westerners Srila Prabbhupada taught were not Sanskrit scholars, in fact, they were drop outs and hippies, addicted to sex, drugs and rockn’roll, still, they were the first ones to take Srila Prabhupada seriously. And because of their faith in Srila Prabhupada they became first class devotees.

This proves that to understand Bhagavad Gita, knowledge of Sanskrit is not required.

What is required, however, to understand Bhagavad Gita, as already nicely explained in other answers to this question, is to receive and learn Krishna’s message from an authorized teacher in the disciplic succession.

That being said, Srila Prabhupada did encourage his disciples to learn Sanskrit, and several of them became proficient Sanskrit scholars. Also, I’m sad to say, a few of them began to second guess Srila Prabhupada’s translations, criticizing them, as a result of which they became useless, and left the movement.

In any case, Srila Prabhupada has translated and explained Bhagavad Gita, so that those who don’t know Sanskrit, like me, for instance, can still understand Krishna’s teachings and live by them. This is the invaluable gift Srila Prabhupada gave to the world - the unadulterated message of Godhead - a message that can be presented in any language.

Which is also why the Srila Prabhupada established the BBT - the Bhaktivedanta Book Trust - to translate his books, like Bhagavad Gita, into all the world's languages.

In fact, he considered the translation and distribution of his books all over the world, the most important part of Iskcon's mission.

Krishna says:

Just try to learn the truth by approaching a spiritual master. Inquire from him submissively and render service unto him. The self-realized souls can impart knowledge unto you because they have seen the truth.

Having obtained real knowledge from a self-realized soul, you will never fall again into such illusion, for by this knowledge you will see that all living beings are but part of the Supreme, or, in other words, that they are Mine.

Even if you are considered to be the most sinful of all sinners, when you are situated in the boat of transcendental knowledge you will be able to cross over the ocean of miseries.

As a blazing fire turns firewood to ashes, O Arjuna, so does the fire of knowledge burn to ashes all reactions to material activities.

In this world, there is nothing so sublime and pure as transcendental knowledge. Such knowledge is the mature fruit of all mysticism. And one who has become accomplished in the practice of devotional service enjoys this knowledge within himself in due course of time.

A faithful man who is dedicated to transcendental knowledge and who subdues his senses is eligible to achieve such knowledge, and having achieved it he quickly attains the supreme spiritual peace.

But ignorant and faithless persons who doubt the revealed scriptures do not attain God consciousness; they fall down. For the doubting soul there is happiness neither in this world nor in the next.

—Bhagavad-gita, 4.34-40