Buuxi weedha soo socota: Prieto wuxuu ku dhashay Segovia, wuxuuna sameeyay kulankiisii ugu horeeyay ee caalamiga ah 1983 European Athletics Junior Championships, isagoo kaalinta shanaad ka galay 10,000 m socodka. Wuxuu kaalinta toddobaad ka galay tartanka lugta ee 20 km ee Koobka Socdaalka Adduunka ee IAAF ee 1985 ka dibna wuxuu ku guuleystay billad naxaas ah tartankaas tartanka fudud ee Yurub ee 1986. Wuxuu isu taagay inuu yahay mid ka mid ah kuwa ugu horreeya ee socodka ah ee Isbaanishka, isagoo ku tartamay Horyaalka Adduunka ee Ciyaaraha fudud 1987 iyo 1991. Prieto wuxuu ku guuleystay billaddiisii labaad ee caalamiga ah 1989 Summer Universiade, halkaas oo uu ku guuleystay billaddii lacagta ahayd ee 20 km oo lug ah oo ka dambeysa Walter Arena ee Talyaaniga. Waxa uu kaalinta 13-aad ka galay
1990 Horyaalkii Adduunka ee Ciyaaraha fudud ee Yurub oo ku dhammaaday hal meel ka hooseeya tan 1991 IAAF World Race Walking Cup.