Due to limited online access to the text, below is an explanation of exactly what a monologue is so you have a better idea of what you are searching for, as well as some tips on searching.
There are four types of monologues: The first is known by the term monologue, the second by the term dramatic monologue, the third by the term soliloquy, and the fourth by the term interior monologue (Encyclopaedia Britannica, "Monologue"). In general, a monologue is a long speech spoken by one character to another character or other characters. The only difference between a monologue and a dramatic monologue is that dramatic monologues are specifically spoken in poems, while a monologue can be spoken in any literary work. There is also a strong similarity between soliloquies and monologues. The difference is that a soliloquy is specifically spoken in a play when the character is alone or thinks he/she is alone. Like monologues, interior monologues can be spoken in any form of literature. Interior monologues can be expressed in four different forms: "dramatized inner conflicts, self-analysis, imagined dialogue, ... and rationalization" ("Interior Monologue"). An interior monologue is essentially a narrative technique used to express the character's inner thoughts and feelings--it is a moment in which the character speaks to himself/herself for a long period of time. To help you better understand interior monologues, it may be helpful for you to look at other known examples in other texts. It has been cited that passages in T.S. Eliot's poem "The Love Song of J. Alfred Prufrock" contains stanzas of interior monologue ("Interior Monologue"). An obvious passage begins at verse 37 and continues until the end of the poem. His use of interior monologue is especially obvious in his imagined dialogue exchanges, such as is found in lines 37-41 and onwards:
... And indeed there will be time
To wonder, "Do I dare?" and, "Do I dare?"
Time to turn back and descend the stair,
With a bald spot in the middle of my hair--
(They will say: "How his hair is growing thin!")
Since you are looking for monologues in a novel as opposed to a play or poem, spoken by the character known as the Poet, whose real name is Alberto, you are looking for either monologues or interior monologues, not dramatic monologues or soliloquies. If you are searching for monologues, you are searching for passages in which only Alberto is the speaker of any dialogue and such a speech could go on from anywhere to one long paragraph to multiple paragraphs or even multiple pages. Looking for such a monologue should be easy because you are looking for very long passages surrounded by quotation marks. Skim through the text. Once you find a long passage surrounded by quotation marks and have noted that the speaker is indeed Alberto, then you know for sure you've found your first monologue. Finding interior monologues may be a bit more difficult because, unless there is imagined dialogue like in T.S. Eliot's poem, you may not have the obvious guiding markers of quotation marks. However, keep skimming through the text to all of the places where you see either the name Alberto or the Poet. Look for places where you see Alberto thinking to himself. Once you find a long passage in which Alberto is thinking to himself, you know you've found an interior monologue.