The Joads and the other migrants who have been pushed out of their homes by the Dust Bowl first hope they can find work and build new lives in California. The "handbills" entice them to go there and paint a rosy picture of the good life.
As Tom says when they arrive and the situation is worse than they anticipated with no work to be found:
It's jus' such a hell of a long ways. An' we kinda hoped we could get work here an' rent a house to live in.
Later, hope moves from hope of individual (family) survival to hope in group solidarity, a major theme if the novel. Tom expresses that communitarian hope as he leaves, envisioning himself as a spirit or apostle of all the people. He says,
Wherever they’s a fight so hungry people can eat, I’ll be there. Wherever they’s a cop beatin’ up a guy, I’ll be there. If Casy knowed, why, I’ll be in the way guys yell when they’re mad an’—I’ll be in the way kids laugh when they’re hungry an’ they know supper’s ready.
He says his spirit will always be, as well, with his family.
Although hope comes to be embodied in worker solidarity in a struggle against the souless world of capitalism, the hope that springs from individual acts of kindness and generosity is never forgotten. It is movingly expressed at the end of the novel when Rose of Sharon feeds a starving man her own breast milk after her baby is born stillborn.