Can lesbians get pregnant without a man?

Depends on how you look at it.

Currently you need a man's sperm in order to make a fetus, so in that sense you do.

However once a man has donated his sperm, a lesbian couple can have it implanted via Intra-Uterine Insemination (IUI) or in vitro.

They're working on being able to create a sperm cell from an egg cell, so soon they will not need a man at all.