Dulko beat Chinese Zi Yan 6-4, 6-4, while the eighth-seeded Li defeated German qualifier Kristina Barrois 6-4, 6-3.
Li lost to Czech Lucie Safarova in last year's Estoril finale.
Three other seeds advances Tuesday. No. 3 Spaniard Lourdes Dominguez Lino beat Portuguese wild card Magali De Lattre 6-1, 6-2; No. 6 Chinese Jie Zheng defeated Belarusian lucky-loser Victoria Azarenka 7-5, 6-4; and No. 7 Frenchwoman Emilie Loit whipped Portuguese wild card Frederica Piedade 6-1, 6-2.