For a person unfamiliar with Spanish poets and poetry, some Spanish love poems are available at DonQuijote.org and Creative-Dating-Ideas.com. For those with knowledge of Spanish poets or who willing to do a little more research, Poets.org is a great database for reading Spanish love poems.
Love is an enduring theme in Spanish poetry. DonQuijote.org lists about a dozen Spanish love poems, including the famous "Llama de amor viva" by St. John of the Cross. Creative-Dating-Ideas.com is also a good resource for reading Spanish love poems by lauded poets, such as Federico Garcia Lorca of Spain and Pablo Neruda of Chile. These sites are a great starting place for those who may be reading Spanish love poems for the first time.
If you have time to do a little digging and want to read more than just a few Spanish love poems from the most well-known poets, Poets.org, a website managed by the American Academy of Poets, is a trove of poetry. Poems such as "Love Opened a Mortal Wound" by Sor Juana Inés de la Cruz, a nun from Mexico, and "XIII" by Peruvian poet César Vallejo are available. Poets.org is still limited in the offerings of Spanish poems specifically focused on the topic of love, but it is a great way to find out some more names in Spanish poetry to continue research elsewhere with more specific poets in mind.