Problem with twoside in article class

Question

I am writing a report in two columns with \documentclass [10pt,twoside]{article}. In the process a problem arose: including the statement \twocolumn the text in two columns jumps to the next page. How do I get the text to print on the same page?

\documentclass[10pt,twoside]{article}
\usepackage[letterpaper,left=0.7in,right=0.7in,top=0.5in,bottom=0.5in,footskip=.2in]{geometry}
\usepackage{graphicx,lipsum}
\usepackage[svgnames]{xcolor}

\begin{document}
\onecolumn
% Cabecera

\begin{flushleft}
\makebox[\textwidth]{\hrulefill}
\end{flushleft}
\begin{minipage}{0.2\textwidth}
%\includegraphics[width=\textwidth]{image} \\ \vspace{3.0cm}
\end{minipage} \hfill
\begin{minipage}{0.77\textwidth}\raggedright
\textbf{\color{olive}\huge\fontfamily{phv}\selectfont Opuntia: cuidado de agaváceas, cactáceas y crasuláceas} \\ \vspace{0.25cm}
{\large Arturo García Flores} \\ \vspace{0.1cm}
{\large Universidad Autónoma Metropolitana--Iztapalapa} \\ \vspace{0.25cm}
\today \\ \vspace{0.25cm}
\lipsum[1]
\end{minipage}%
\begin{flushleft}
\makebox[\textwidth]{\hrulefill}
\end{flushleft}

\twocolumn

\section*{Introducción}

\noindent \lipsum[1-7]

\end{document}

I used the multicol package, but for some reason the text doesn't wrap as I type.

I also used \documentclass [10pt,twocolumn]{article}, but the text in two columns is printed over the text in a column shown in the image (and which is a minipage).

Answer 1

If I understand the question correctly you can either place the initial text in the optional argument of \twocolumn so that it spans the columns

\documentclass[10pt,twocolumn]{article}
\usepackage[letterpaper,left=0.7in,right=0.7in,top=0.5in,bottom=0.5in,footskip=.2in]{geometry}
\usepackage{graphicx,lipsum}
\usepackage[svgnames]{xcolor}

\begin{document}

\twocolumn[{
% Cabecera
\begin{flushleft}
\makebox[\textwidth]{\hrulefill}
\end{flushleft}
\begin{minipage}{0.2\textwidth}
%\includegraphics[width=\textwidth]{image} \\ \vspace{3.0cm}
\end{minipage} \hfill
\begin{minipage}{0.77\textwidth}\raggedright
\textbf{\color{olive}\huge\fontfamily{phv}\selectfont Opuntia: cuidado de agaváceas, cactáceas y crasuláceas} \\ \vspace{0.25cm}
{\large Arturo García Flores} \\ \vspace{0.1cm}
{\large Universidad Autónoma Metropolitana--Iztapalapa} \\ \vspace{0.25cm}
\today \\ \vspace{0.25cm}
\lipsum[1]
\end{minipage}%
\begin{flushleft}
\makebox[\textwidth]{\hrulefill}
\end{flushleft}

}]

\section*{Introducción}

\noindent \lipsum[1-7]

\end{document}

Or you can use multicol to allow switching to two-column mid-page

\documentclass[10pt]{article}
\usepackage[letterpaper,left=0.7in,right=0.7in,top=0.5in,bottom=0.5in,footskip=.2in]{geometry}
\usepackage{graphicx,lipsum,multicol}
\usepackage[svgnames]{xcolor}

\begin{document}


% Cabecera

\begin{flushleft}
\makebox[\textwidth]{\hrulefill}
\end{flushleft}
\begin{minipage}{0.2\textwidth}
%\includegraphics[width=\textwidth]{image} \\ \vspace{3.0cm}
\end{minipage} \hfill
\begin{minipage}{0.77\textwidth}\raggedright
\textbf{\color{olive}\huge\fontfamily{phv}\selectfont Opuntia: cuidado de agaváceas, cactáceas y crasuláceas} \\ \vspace{0.25cm}
{\large Arturo García Flores} \\ \vspace{0.1cm}
{\large Universidad Autónoma Metropolitana--Iztapalapa} \\ \vspace{0.25cm}
\today \\ \vspace{0.25cm}
\lipsum[1]
\end{minipage}%
\begin{flushleft}
\makebox[\textwidth]{\hrulefill}
\end{flushleft}

\begin{multicols}{2}

\section*{Introducción}

\lipsum[1-7]

\end{multicols}

\end{document}