Fuerte can set some fruit alone, but it does better with a partner. A compatible partner usually improves fruit set and crop consistency. It flowers in bloom group type-b, which is Type B bloom, so a partner has to be flowering at the same time to be any use. Usually grown in USDA zones 9-11.
The good news is you have real choices here. The strongest partners are Hass, Pinkerton, and Reed. Any one of them is enough to get fruit set going. Plant Type A and Type B avocado varieties close enough for bees to visit both trees during the same bloom period. In small gardens, nearby spacing is usually more useful than distant orchard spacing.
To put that into practice: at a minimum, one grafted avocado can sometimes fruit alone, especially in mild climates with strong bloom overlap. Better still, pair one Type A and one Type B variety with similar bloom timing for steadier fruit set and better backup in cool or uneven bloom weather. If you only have room for one tree, choose a reliable self-fruiting variety and focus on frost protection, drainage, and pollinator activity before assuming another tree is required.