Looks like lack of pruning, plus not enough sun. It also looks like the cement is pretty close to the trunk, making it hard to get water to the roots. Zone 10 doesn't get many chill hours, which makes it harder to grow certain types of peaches. You need low chill varieties. http://mgorange.ucanr.edu/Edible_Plants/?uid=88&ds=530

I agree that a proper pruning is needed; and as stated, needs a certain hours of cold-chill to set fruit. With the pruning: If it's not properly pruned the fruiting "twigs" could be being removed and thus reducing the harvest.