Do bilingual people learn in both languages?

Truly bilingual people -- those who are completely fluent in two languages-- report that they can learn concepts and material in either language, but that the situation will determine which one they use. For example, if they are taking a math class in English, rather than translating each concept into their native language they think about it in English. However, if later asked to explain the material in their native language, they will tend to recall it in English first and then translate.

Is learning merely a function of memory?

In the sense that learning depends on storing, retrieving, and using information about our world, then yes, learning is largely a function of memory. Learning is not merely active memorizing, however, without any conscious effort on our part. For example, conditioned responses develop in an automatic fashion. Similarly, much of our social knowledge about acceptable behavior or racial stereotypes is absorbed throughout childhood from various subtle cues and experiences.