How you can tell they do not speak English: "Do you know where the running shoes are?" "Yes." Can you tell me what colors are available?" "Yes." "How many different kinds do you carry?" "Yes."
My point is that if the associate gets someone to translate, treat them as a translator and ask the associate. Smile, give him/her room to be told what you are asking. Thank the translator for helping you communicate, thank the associate for the information.
"When will I know that this mango is ripe?" Translator is called over. Me: "Thank you for helping us. I was asking him/her about this mango." Look at the associate and repeat, "When will I know that this mango is ripe?" The translator SHOULD translate and then translate the associate's answer.
In my area we get a lot of Haitians and Hispanics and they know who in the store can help them out. Their translator is also interested in having them learn English so they eventually won't need a translator so these interactions can be beneficial to the employee in making progress in English as well as getting your job done.