For some of the best Pho Bò I have ever tasted, go to the north/west corner of Nguyèn Thi Minh Kai and Nguyên Thien Thuat streets. It is right across from a shoe shop.
I have had pho there since 1995 and in my humble opinion there is no better. Pho Bò, in case you don't know, is beef noodle soup. The owner serves it with just the right spices, leaves and you'll feel your're in heaven.
On the same street, heading towards the beach, on the right side after passing Nha Trang Seafood Restaurant (which I do not recommend), there is some nice sticky rice to be had. This is just prior to reaching the large piazza on the beach.